Russia amassed more than 100,000 troops on Ukraine’s eastern border and in illegally annexed Crimea in April. It billed these provocative movements as snap readiness exercises and eventually announced their withdrawal. To date, however, most of them remain, appearing poised to invade Ukraine. Whether Moscow is preparing for an invasion in earnest, posturing in anticipation of NATO’s Defender Europe 21 exercise that began this month, testing the new Biden administration, diverting attention from Russia’s domestic troubles, or some combination of the above remains unclear. One thing is certain: Russia has a superior military force and political resolve to unleash violence in Ukraine if it finds it politically expedient.

This is not only a persistent threat to Ukraine, a strategic partner of the United States, but also to the security of the NATO alliance and thus to core U.S. interests. In its recent threat assessment, the U.S. Intelligence Community recognized that Russia will continue to take advantage of power vacuums in order to advance its interests, undermine the interests of the United States, and weaken Western alliances. Ukraine is just such a power vacuum. The question is, how to effectively fill it and reduce the space in which Russia can continue to play its destructive games.

In Kyiv, anxieties ran high as the Russian buildup continued. The city administration released a map of bomb shelters to prepare for the eventuality of Russian air raids. Ukrainian officials also sounded the alarm internationally. Ukraine’s Ambassador to Germany Andriy Melnyk called for the West to supply advanced weapons to Ukraine and stated that the only way to prevent a military attack by Russia is for Ukraine to join NATO. “The only other option,” Melnyk added, “[is] to arm ourselves, and maybe think about nuclear status again.”

NATO membership, once a minority faith in Ukraine, garnered the support of the majority of Ukrainians after Russia’s invasion in 2014. The conflict has claimed more than 13,000 lives and evaded attempts by Germany and France to mediate its resolution. The first question Ukrainian President Volodymyr Zelenskyy wanted to ask U.S. President Joe Biden was, why isn’t Ukraine a NATO member yet?

Russia’s aggression in 2014 also prompted calls to reverse Ukraine’s decision to relinquish the world’s third-largest nuclear arsenal it inherited from the collapsed Soviet Union. In 1994, under U.S. and Russian pressure and to be on the right side of history, Ukraine joined the Nuclear Nonproliferation Treaty (NPT) in exchange for security assurances from the nuclear states in what became known as the Budapest Memorandum. Now that Russia, one of the signatories, violated the letter and the spirit of the memorandum, some Ukrainians claim the deal is off.

In our view, neither formal NATO membership nor nukes are fitting security options for Ukraine. To secure its borders and achieve sustainable peace and stability in Europe, Ukraine should forge a treaty-based strategic alliance directly with the United States.

Here is why.

“No” to NATO, “Yes” to the NPT

Ukraine’s membership in NATO is not a good idea. NATO has now grown to 30 members that still make decisions by consensus. There are differences in opinion among the members about the gravity of the Russian threat and the desirability of Ukraine’s membership in the alliance. A decision to admit Ukraine and assist it in defense against Russia will likely be mired in disagreements and delays. And NATO’s eastward expansion, in alleged breach of disputed late-Cold War promises of restraint by the United States to the Soviet leadership, has become a trope for explaining and sometimes justifying Russia’s belligerence. The talk of Ukraine’s potential membership in the alliance only fuels the misguided narrative of Western culpability in Russia’s transgressions.

Ukraine’s withdrawal from the NPT and a launch of a costly nuclear-weapons program is an even worse idea. It would increase the risk of Russian military escalation, with much the same justification as the United States used for its 2003 invasion of Iraq. Moreover, developing nuclear weapons takes time, which Russia could easily use to sabotage a Ukrainian nuclear arms program (think Israel’s actions in Iran). Most importantly, by undermining the nuclear nonproliferation regime, Ukraine would inevitably lose American and European support, upon which it relies in its struggle with Russia.

Things, however, cannot be left as they are.

The post-Cold War settlement in Europe left Ukraine in a geopolitical power vacuum. And as every student of politics knows, power abhors a vacuum. Ukraine could have done a better job of providing for its own security by building a better-governed state with better military defenses. But even under the best of circumstances, Ukraine cannot withstand a Russian military onslaught alone. The alternative is for Ukraine to become a Russian satellite, if the Ukrainians agreed. But they don’t. And so Europe’s eastern flank remains permanently exposed to the danger of a military conflict, Russia’s hand remains on the escalation dial, and the West remains reactive rather than proactive.

Major Non-NATO Ally

The only way to turn the tables and fill the security vacuum is to forge a U.S.-Ukrainian strategic alliance. Such a strategic alliance should start with the United States granting Ukraine major non-NATO ally (MNNA) status as soon as possible. There are 17 countries that are currently designated as MNNA: Afghanistan, Argentina, Australia, Bahrain, Brazil, Egypt, Israel, Japan, Jordan, Kuwait, Morocco, New Zealand, Pakistan, the Philippines, South Korea, Thailand, and Tunisia. (Taiwan is another country that is effectively an MNNA, although it is not formally designated as such.)

Making Ukraine an MNNA would put the existing defense cooperation between the United States and Ukraine on a firm formal footing and stake its strategic significance to the United States. Since the U.S. Congress passed the Ukraine Freedom Support Act in December 2014, the United States has provided more than $1.6 billion in security assistance to Ukraine, including anti-tank Javelin missiles in 2017. This is significant, although, for comparison, the United States provides about $3 billion in military aid to Israel annually. The United States and its allies have helped train the Ukrainian military, reform the Ukrainian defense sector to bring it up to NATO operational standards, and conducted joint training exercises. U.S. Secretary of State Antony Blinken, visiting Kyiv in early May, condemned Russia’s “reckless and aggressive” actions and reaffirmed that the United States will continue to strengthen its security partnership with Ukraine.

The MNNA status would do exactly that. It would allow the United States to intensify the effort to reform and train the Ukrainian military and make it fully interoperable with the U.S. European Command. It would also bring additional benefits in defense trade, such as the transfer of sensitive military technologies and collaboration on defense projects that would boost Ukraine’s legacy Soviet defense industry and enable it to supply Ukraine’s armed forces with state-of-the-art equipment. Most importantly, it would serve as a powerful message to Moscow that the U.S. commitment to Ukraine’s security — and to stability on NATO’s border — is permanent and non-negotiable.

On the U.S. side, conferring the MNNA status is an executive decision, not requiring the consent of the Senate. It would, however, require negotiating and signing an agreement on mutual protection of sensitive technology. After the meeting with Blinken, Zelenskyy mentioned that a “very serious” bilateral agreement was discussed. While no further details were divulged, if the Biden administration is moving toward an MNNA agreement, then it is on the right track.

Once Ukraine becomes an MNNA, the United States could consider opening a permanent military base, or lease an existing military facility on Ukraine’s territory, like it does in Jordan and Israel. The United States could also reserve an option to deploy a small trip-wire unit of a few hundred troops to Ukraine, in proximity to the line of contact, to deter regular Russian detachments from crossing the internationally recognized Ukrainian border. While the Ukrainian army is there to defend against any Russian invasion should it happen, the U.S. trip-wire force would be there to deter it in the first place.

An advantage of the bilateral U.S.-Ukraine MNNA framework is that such U.S. deployments would not be constrained in the same way NATO deployments would be. In the 1997 NATO-Russia Founding Act, NATO pledged that “in the current and foreseeable security environment,” the alliance would not to carry out “additional permanent deployments of substantial combat forces.” While it is debatable whether the post-2014 security environment is still comparable to what was “current and foreseeable” in 1997, NATO has to contend with this pledge when considering deployments in Poland, for instance.

If Ukraine performs as a capable and responsible ally, the United States should consider a next step — signing a mutual defense treaty, the kind the United States has with Australia, Japan, New Zealand, the Philippines, and South Korea. A U.S.-Ukrainian defense alliance would be a mutually beneficial arrangement. Ukraine is a valuable security asset for the United States and NATO allies. Ukraine’s military has made remarkable progress since 2014, when it struggled to scrape up some 5,000 capable soldiers and as many volunteers to counter the Russian invasion. Today, it is 250,000-strong, about the size of NATO Eastern allies — Poland, Romania, Hungary, Bulgaria, and the three Baltic states — combined. Global Firepower Index ranks Ukraine’s military number 25 in the world, just two places behind Poland, the only other Eastern European state in the top 30. Importantly, Ukraine is the only European country with real combat experience in defending itself from Russian forces, which are ranked number two by the same index.

For Ukraine, this is the only feasible way to provide for its security as long as Russia continues to harbor unwelcome designs on its neighborhood. The fear of losing U.S. support and a promise of a mutual defense treaty should prevent Ukraine from backsliding on democratic governance and free-riding on the U.S. security guarantee, as is the case of Hungary or Turkey in NATO. Finally, formal U.S. backing will strengthen Ukraine’s position in negotiating a peaceful settlement of the conflict in the Donbas and the de-occupation of Crimea and advance a sustainable resolution that corresponds to long-term security interests of Ukraine and Europe.

Regaining the Initiative

A U.S.-Ukrainian alliance will not please the Kremlin, which will consider it an act of further encirclement by the West. The United States should not be dissuaded by the fear of exacerbating the Kremlin’s paranoia, which seems to be innate and resistant to evidence. In other words, even disengaging from Ukraine entirely will not convince Kremlin’s leaders, who see the CIA’s hand in every street protest in the post-Soviet space, that the West is not out to get them.

A U.S.-Ukrainian alliance will not radically alter the perceptions of Russian leaders; rather, it will only confirm what they already believe. But it will impose real costs on Russia’s ability to escalate the situation in Ukraine’s East and the strategic Black Sea region, effectively tempering the Kremlin’s appetite for adventurism abroad. With narrowed options for diversion tactics, Russia’s leaders might become more accountable at home, where pressure for greater freedom and better governance is building.

While achieving sustainable security and prosperity in Ukraine and imposing real costs for disrupting it is squarely in the interests of the United States, Europe, and Ukraine, long-term it will also serve the interests of the Russian people.

IMAGE: The US Legend-class national security Coast Guard Cutter Hamilton is seen in the port of Odessa on the Black Sea after conducting joint exercises according to NATO standards with the Ukrainian Navy ship Starobelsk on May 11, 2021 in Odessa, Ukraine. As part of the efforts to bolster NATO maritime partnerships, the US Coast Guard conducted maritime law enforcement, search and rescue, and ship-handling operations with Ukrainian navy vessels. (Photo by Pierre Crom/Getty Images)