Explaining the Debate of Ukraine’s Prospects for NATO Membership

By Delia Liesenfeld

Introduction

Since the end of the Cold War, there have been discussions over Ukraine’s prospects for joining the North Atlantic Treaty Organization (NATO). NATO is a political and military alliance to guarantee the security of its members in the North Atlantic region. NATO was initially founded in 1949 to deter Soviet expansionism, prevent the revival of nationalist militarism in Europe, and encourage European political integration. Today, NATO focuses on peacekeeping, collective defense, and responding to international crises. While the alliance was founded by 12 countries, it has expanded to 32 members, including the United States and Canada, and has reached all corners of the European continent. With Russia’s invasion of Ukraine in 2022 and current peace negotiations, Ukraine’s membership is now an issue of great debate. But what does Ukraine’s history with NATO look like? Do the pros for membership outweigh the cons? Are there alternative solutions to NATO membership that still allow the West to support Ukraine? And what do prospects look like for Ukraine’s membership moving forward? 

Ukraine’s History with NATO

Since the collapse of the Soviet Union, NATO members have been determined to integrate Ukraine under their influence; as a nation between Russia and Eastern Europe, Ukraine’s sovereignty and position as a buffer state are critical for European security. A sovereign Ukraine maintains the balance of power in Europe, as this prevents further military aggression and territorial disputes on the continent. Furthermore, Ukraine has historically served as a major transit route for Russian natural gas supplies to Europe, so Ukraine’s sovereignty is vital for European energy security. This has been the foundation of Ukraine’s relationship with NATO. According to Article 10 of NATO’s founding treaty, NATO is open to any European country capable of assuming the commitments and obligations associated with membership, including promoting the principles of the Washington Treaty; contributing to the security of the Euro-Atlantic area; and meeting political, economic, and military criteria. As a European country, Ukraine is eligible. In 1991, Ukraine joined the North Atlantic Cooperation Council, a forum for dialogue between NATO Allies and former Warsaw Pact adversaries. In 1994, Ukraine was one of the first former Soviet states to join NATO’s Partnership for Peace, aiming to develop political and military cooperation between NATO and countries to its east. This was also the beginning of Ukraine’s implementation of NATO standards. From 1995 to 2003, NATO conducted annual training exercises with the Ukrainian military at its Yavoriv base, deepening interoperability, cooperation with NATO forces, and the partnership. By cooperating with NATO forces, Ukraine demonstrated its reliability and military capabilities. 

In 2002, Ukraine’s President Leonid Kuchma signed an action plan committing Ukraine to join the alliance. At the April 2008 NATO Bucharest Summit, the heads of NATO member states announced Ukraine and Georgia would one day become members. However, Allies could not reach a consensus on whether to issue Ukraine a Membership Action Plan (MAP). While the U.S. supported granting Ukraine a MAP, France and Germany opposed on the grounds that this would provoke Russia by challenging its security. The following summer, Putin ordered planes and tanks into Georgia, halting NATO’s enlargement to former Soviet Republics. Ukraine further backtracked in 2010 when Victor Yanukovych was elected president of Ukraine and sought to improve relations with Russia while demonstrating no interest in bringing the country closer to NATO. In 2014, Russia illegally annexed Crimea, part of Ukraine’s territory, leading NATO to provide practical assistance and support for capacity-building in Ukraine. Since then, NATO has increasingly provided Ukraine with support. 

In 2021, tensions once again began to increase in the region. United States officials accused Russia of massing troops on the Ukrainian border to prepare for future invasion, while Russia accused Ukraine of threatening it by positioning troops and heavy weapons on its border. In December 2021, the Russian deputy foreign minister presented NATO with an unrealistic wishlist to diffuse tensions, including a ban on Ukraine’s NATO membership. When NATO declined, Putin invaded Ukraine. Since the full-scale invasion, NATO has increased its training and education of Ukrainian forces in NATO countries. Prior to the invasion, less than half of NATO countries provided military assistance to Ukraine, and many of the weapons provided were second-hand and could not be reasonably used against Russia. Now, NATO members’ provision of military assistance has expanded with 29 countries contributing, and the quality of assistance has improved, providing newer weapons that can be used effectively against Russia. Leading up to the NATO Vilnius Summit in July 2023, many allies, including Poland, the Baltic States, the Nordic States, France, and Britain, proposed that Ukraine be invited to join NATO, while officials in the US and Germany disagreed. Therefore, Vilnius sought to reaffirm Ukraine’s future in the alliance through fast-tracked membership, but no clear timeline for accession were set. Vague terms stated membership would be extended “when Allies agree and conditions are met.” At the Washington Summit in July 2024, Ukraine’s future within NATO was nominally reaffirmed, but once again, no criteria or timeline for Ukraine’s accession was established. This summit instead focused on addressing Ukraine’s near-term military needs. By the final day of the summit, Ukraine had concluded bilateral security agreements with 23 countries and the European Union. These agreements commit countries to support Ukraine in the conflict with Russia by helping the country develop stronger defense capabilities and take other defensive actions. These agreements were seen as a political signal that Ukraine is important to the West, will continue to receive support, will receive cooperation on reforms to help the country join the EU and NATO in the future, and ultimately act as a bridge to Ukraine’s membership in NATO. 

To increase prospects for NATO membership, Ukraine has focused on interoperability with NATO forces and democratic consolidation. Under the Partnership Interoperability Initiative, Ukraine has been advancing its interoperability capabilities through cooperation, dialogue, joint exercises, and NATO-led operations with NATO forces. Ukraine is also following dozens of NATO doctrines and guidelines in training, logistics, and planning. For example, Ukraine implemented NATO’s operational symbols, colors, military ranks, and uniforms while providing some of its armed forces for joint peacekeeping operations and military exercises. In 2020, Ukraine was named the sixth “Enhanced Opportunities Partner" of NATO, which increased consultations on security issues and granted Ukraine access to programs, exercises, and information. 

While Ukraine has struggled to become a full democracy, it exemplifies a growing societal pushback against authoritarianism and a desire for a free, democratic future with three events: the 2004 Orange Revolution, the 2014 Euromaidan Revolution, and the 2022 full-scale war. During the 2004 Orange Revolution, protests emerged after Viktor Yanukovych, the pro-Russian candidate, was declared the winner of the 2004 presidential election. Weeks of demonstrations occurred due to accusations of fraud. In December 2004, the election was declared invalid, a new election was held, and Viktor Yushchenko, the anti-corruption candidate, was declared the president. 

During the 2014 Euromaidan Revolution, hundreds of thousands protested Viktor Yanukovych’s move to discard an agreement to bring the country closer to the EU, instead favoring closer ties with Russia. Police and government security forces fired on protestors, leading to sanctions by EU leaders. Ultimately, an EU-brokered agreement between Yanukovych and opposition leaders called for early elections and the formation of an interim unity government. The 2004 constitution was restored, and Yanukovych fled the country. 

Following the 2014 Euromaidan Revolution, Ukraine enacted reforms to combat corruption. For example, the National Anti-Corruption Bureau of Ukraine was founded in 2014 to detect, investigate, and prevent corruption, while the National Agency on Corruption Prevention was created in 2016 to develop and implement anti-corruption policies. With the full-scale war and influx of aid, Zelenskyy has accelerated anti-corruption enforcement. For example, in 2023, Zelenskyy removed many of his administration members due to suspicions of misconduct. Nevertheless, corruption still remains, with some of Zelenskyy’s closest allies accused of misusing $100 million from Ukraine’s nuclear energy body, Energoatom. Estimates show that Ukraine is about halfway through its anti-corruption journey. 

Current Barriers

The predominant reason Ukraine cannot join NATO is that if it were to do so while the war with Russia is ongoing, this risks triggering the Article V obligation if Russia strikes Ukraine. Article V states that an attack on one member is an attack on all, obligating allies to assist the attacked nation through whatever action is deemed necessary, which may include armed force. If Article V is invoked for Ukraine, the alliance may find itself in a full-scale war against a nuclear superpower. Because of this circumstance, as long as the war is ongoing, unanimity will not be reached among all NATO members about Ukraine’s accession, as allies are eager to avoid a war with Russia. In addition, because Ukraine is at war, it is unclear what a post-war Ukraine might look like. Because of this, it is too soon to offer Ukraine definitive NATO membership. There are fears among NATO allies that if a specific time is given for accession, this may discourage Putin from agreeing to end the war, as he wants to prevent Ukraine from ascending. Therefore, it is not an option to directly state that Ukraine can join as soon as the war is over. Finally, President Donald Trump’s return to the White House further complicates this process. President Trump has shown ambivalence toward the outcome of the war and reluctantly supports Ukraine. Consequently, President Trump’s anti-NATO, pro-Russian rhetoric means Ukraine’s membership in NATO for the time being is almost unimaginable. For these reasons, Ukraine cannot join NATO at this time. 

But now, conditions are shifting, so the NATO question is more relevant. In December 2025, talks were held between European officials, Ukrainian officials, and US officials aimed at negotiating a peace plan to end the war. While the Trump Administration has drawn up peace agreements for the end of the war, neither side is likely to sign them due to territorial disagreements, leading to the current peace negotiations. The US has pushed Ukraine to accept concessions to Russia, including ceding territory, while Zelenskyy has refused to cede territory to Russia. However, Russia is only willing to accept maximalist demands for the end of the war, meaning Ukraine needs to surrender territory to Russia. Moreover, Zelenskyy has stated he is ready to give up demands for NATO membership in return for security guarantees from the US and Europe similar to those present in Article V.

Arguments for Ukrainian NATO Membership

Peace and security for Ukraine are unsustainable without NATO membership and Article V commitments. Putin’s continued violations of Ukrainian territorial sovereignty, like the 2014 invasion of Crimea and the 2022 full-scale invasion, demonstrate that he will not stop without a proper deterrent. With Article V guarantees and the backing of a 32-member alliance, this would act as a strong deterrent against further Russian aggression. In addition, security for both Ukraine and Russia would increase, as Ukraine would be barred from attacking Russian territory due to concerns about escalation. Ukraine as a NATO member would strengthen European security by minimizing the likelihood of a prolonged war, total Russian victory, or a fragile peace deal without security guarantees. Without Ukraine in NATO, Europe is more unstable in the long term. Russia's invasion of Ukraine has fractured Europe’s security landscape. If Ukraine is not admitted into NATO, this lowers the risks of a future Russian attack or invasion, as there is no guaranteed Western response. Furthermore, Ukraine would be incorporated into NATO’s political-military structures, meaning Ukrainian leaders would need to coordinate with allies militarily, bolstering interoperability and European defense cohesion. By joining NATO, its members have greater input in Ukraine’s post-war development and reconstruction. 

NATO membership is more likely to deter Russian aggression. Russia has not invaded a NATO member state in the 76 years the alliance has existed, meaning Article V acts as an effective deterrent. Russia has also respected new NATO allies, avoiding confrontation with former Soviet countries on its border, like Finland and the Baltic States. In the invasion, Russia has been careful not to let the war spread to NATO members and has been quick to deny any involvement when missiles have strayed into NATO territory. By bringing Ukraine into the alliance, Russia would likely be deterred from invading again, as allies may send military equipment to Ukraine, impose sanctions, respond with force, or take any other action deemed necessary. In addition, it is unrealistic to assume Russia can be deterred and Ukraine kept secure in the long run without NATO membership. Russia has acted aggressively toward Ukraine frequently, with the 2014 annexation of Crimea and increased tensions leading up to the 2022 invasion. This demonstrates there is no security in neutrality. To ensure absolute security for Ukraine, NATO membership is necessary to deter Russian aggression. 

Finally, inviting Ukraine into the alliance would make the world safer for democracy by demonstrating that democracies will not allow Russian aggression to win. This would decrease future authoritarian imperial violence. Not including Ukraine sends the opposite signal.

Arguments Against Ukrainian NATO Membership

If Ukraine is invited to join NATO, it will increase the risk of a war with Russia. Ukraine’s joining of NATO is considered a red line for Russia. Russia is concerned about NATO expansion on its border, with enlargement into Eastern Europe considered an “anti-Russian project.” Extending NATO membership to Ukraine would preserve the spark that contributed to the start of the war, potentially provoking a future crisis that could turn nuclear. Likewise, membership itself is insufficient to deter Russia and may lead it to test NATO’s resolve and Article V commitments. This would mean NATO countries would need to decide whether to respond and if they want to risk direct engagement with Russia. If NATO does not respond, then this undermines the alliance’s credibility. Additionally, if there is a belief that Ukraine will be offered NATO membership once the war ends, then Russia may continue fighting and refuse to negotiate to avoid this possibility. Because of Ukraine’s geographic location, it will face backlash and aggression from Russia with or without NATO membership. This means it is preferable for NATO countries to focus on military assistance, which is less costly and less risky. 

Secondly, some argue that US security does not depend on Ukraine’s security, and Ukraine is strategically unimportant as it is not essential to maintaining the balance of power. Even with gains in Ukraine, Russia is not poised to dominate Eurasia, as the balance of power favors Europe in terms of GDP, military spending, active military personnel, and population. Furthermore, the US has no need to worry about the norm of territorial integrity, as it is secure with nuclear weapons, docile neighbors, and ocean barriers. Russia is unlikely to use Ukraine as a launchpad to bring back the Soviet Empire, because Russian interest in Ukraine is unique, specifically pertaining to preventing the country from joining NATO. Ukraine has already protected its own territorial integrity by causing Russia to suffer from the invasion. 

Finally, Ukraine’s membership would greatly affect NATO by forcing the alliance to assess how to secure Ukraine’s 2,000km border with Russia, more than doubling the amount of NATO territory bordering Russia while defending Ukraine’s internal territory. Additionally, NATO will need to deploy forces to Ukraine to uphold the country’s territorial security and deter Russia. It will also be necessary to extend defense to Ukraine’s airspace through missile defense and the deployment of aircraft, because Ukraine’s air force will be unable to hold off a Russian attack alone due to its small size. NATO will need to increase Black Sea security, which plays a vital economic role in exporting Ukrainian goods, particularly agricultural, and will be essential for rebuilding Ukraine after the war. The Black Sea is a strategic priority for NATO countries Bulgaria, Romania, and Turkey, however, since the annexation of Crimea, Russia has claimed the sea as part of its exclusive economic zone and has aimed to take control of the sea in the past. Therefore, Russia will likely take an aggressive stance in the Black Sea if Ukraine joins NATO, meaning NATO will need to respond. By granting Ukraine membership, NATO should also expect Russia to intensify hybrid attacks and other military operations against Eastern European NATO members. All of these operations are likely to accrue additional costs for NATO members. Finally, victory is likely to end in a stalemate where Russian forces still occupy Eastern Ukraine with a ceasefire in place, rather than a decisive military victory by Ukraine. This brings the triggering of Article V into a grey zone, a great risk for NATO allies.   

Alternative Solutions and Their Effectiveness

Some temporary and permanent alternatives to NATO membership have been offered, but many of them do not work in the long term, so they are not a permanent solution to the NATO question. To begin, Ukraine could be accepted as a member with a geographically limited Article V. If the war ends in an ambiguous scenario where Russian forces remain in parts of Ukraine, Article V could only cover territory currently held by Ukraine. There is a precedent to this. In 1955, when West Germany ascended into NATO, Article V only covered that portion of the country. However, West Germany was different. During the Cold War, there was no ambiguity about the border that should be defended. Furthermore, Russia has proven willing to use large-scale military force to annex territory and destroy Ukraine’s statehood, something not present with West Germany. Thus, limited Article V guarantees would be ineffective. 

Countries could aim to build Ukraine’s military capacity over the long term, following the Israel Plus Model. “The US provides nearly 4 billion dollars worth of military aid every year to Israel” (Wesslau 8) while focusing on joint development of military technology, but the US does not send troops when Israel is attacked by missiles. A similar strategy could be followed in Ukraine by building a sustainable security partnership. This strategy aims to ensure Ukraine is sufficiently well-armed to defend itself and thereby deter Putin from another attack. Ukraine’s international partners could make legally binding, open-ended commitments to build up Ukraine’s military industrial production base, to provide Ukraine with modern weapons and ammunition, to share intelligence, to undertake training and exercises, strengthen Ukraine’s hybrid and cyber defense, and provide aid. But if this strategy were implemented, it should go hand in hand with NATO membership, as Ukraine could otherwise become a considerable military power, but without the restraints provided by NATO. Allied countries have no legal bounds to constrain non-members, meaning any negative military action taken by Ukraine cannot be prevented but is directly funded by partner countries. NATO membership would be cheaper than an open-ended, long-term commitment to fund Ukraine’s military capacity, as under NATO, funding comes from a budget and common funds, as opposed to individual commitments. In addition, the Israel model may not be preferable, as the security relationship would exert massive influence over NATO's own choices, as Ukraine would not be integrated into NATO’s political-military structure and therefore could exert non-traditional influence. Finally, this option may not truly deter Russia, as, unlike Israel, Ukraine has no nuclear weapons and thus does not have significant deterrent capacity against another nuclear power. 

Another alternative is to implement bilateral security guarantees. Bilateral security guarantees are promises between two countries to provide military and political support if one is attacked. These could be in the form of a coalition of key states to use air power to protect western Ukraine while providing partial security guarantees, committing to defend Ukraine with air strikes on Russian military targets inside Ukraine. This commitment would deter Russia from trying to attack Ukraine by land. Yet any security guarantees by NATO allies may not be credible, as no country was willing to fight for Ukraine when its independence was at stake due to Russia’s invasion. In addition, it would impose a high cost on the country making the security offer, raising questions about burden sharing and free-riding. Even so, NATO’s mutual defense clause is more formidable than bilateral security guarantees with a few countries, as it entails an automatic response by an organization of 32 countries. 

A final alternative is to provide assistance to Ukraine instead of NATO membership. The United States currently provides security assurances and political commitments to provide long-term military and financial assistance to Ukraine. As of July 15, 2025, the US's total budget for Ukraine reached $175 billion, $128 billion directly to the Ukrainian government, demonstrating strong willingness and capability in this capacity. The US could continue to provide Ukraine with arms and training so Ukraine can defend itself. Arming Ukraine indefinitely would lower annual costs, as Ukraine should be able to maintain the capability it has gained. There could be an explicit NATO commitment of weapons deliveries to Ukraine for as long as possible, signalling to Russia that NATO is in the fight for the long haul and Russia cannot outlast Ukraine. However, Ukraine then loses the NATO benefits previously mentioned, and states must incorporate funding for Ukraine as part of their budgets, as opposed to the NATO budget. Overall, while many of these alternate solutions may be effective in the short term, they are not effective long-term solutions to the NATO question.

Conclusion

Ukraine’s NATO membership prospects are complex. With 30 of the 44 European countries being NATO members, it is likely that Ukraine will be invited to join the alliance in the future. Nevertheless, this future is likely to be far off. Now that European leaders have seen what Putin is capable of, as opposed to empty threats of invasion, there will likely be greater caution in admitting Ukraine to NATO. For the time being, NATO allies will most likely try to protect Ukraine through security guarantees. European leaders have already stated that they are prepared to send troops to Ukraine to secure the country once the war is over. Despite these moves, NATO membership is not off the table for Ukraine. Ukraine’s long history with Ukraine, from training sessions to promises for future membership, signals that NATO allies support Ukraine’s accession, but the main question is when.