On Monday, Turkey officially dropped its opposition to Sweden’s pending membership in the North Atlantic Treaty Organization (NATO), making it all but official that Sweden would be joining the group.

Interest in NATO membership has greatly risen in parts of Europe in the wake of Russia’s invasion of Ukraine, which has been perceived as a larger attempt by Russian President Vladimir Putin to restore Russia’s Cold War-era boundaries.

But one sticking point in the membership drive for NATO has been Ukraine itself, which is still at war with Russia and is seeking a diplomatic asylum of sorts. Membership in NATO could end up resulting in the other member states being dragged into the war, escalating an already precarious situation.

President Joe Biden has warned NATO against allowing Ukraine to join the alliance for that very reason, though that stance puts him at odds with some of our closest allies.

Biden on Tuesday sought to smooth over any disagreements when NATO Secretary-General Jens Stoltenberg greeted him at the summit. “We agree on the language that you propose, relative to the future of Ukraine being able to join NATO,” Biden said. “And we’re looking for a continued united NATO.”

U.S. diplomats handling communiqué negotiations have tried “to bridge the gap among allies and reach consensus,” said a U.S. official. “So as a result, we have sought to find agreed language that reflects Ukraine’s progress on its Euro-Atlantic aspirations, which all allies can agree to.”

Biden’s outspoken concerns with Ukraine’s push to join NATO—he has raised the prospect that doing it too early could start World War III—have frustrated officials in Kyiv and beyond.

It isn’t just Ukraine. Lithuanian President Gitanas Nausėda said on Monday that “Inviting Ukraine to join NATO would be our strategic responsibility and would firmly link Ukraine to the Euro-Atlantic security architecture.”

He also said, more succinctly, that “Ukraine deserves to be invited.”

The problem for NATO is the core agreement of the alliance: That an attack on one member is an attack on all members. That mutual defense pact was a central philosophical idea when NATO was first formed – once again in the face of a Russian threat. But most of the world is reluctant to see World War III break out, and Biden, in particular, has shown his aversion to armed conflict, having made ending the war in Afghanistan an early goal.

However, the results of that event were nothing short of disastrous, and the Biden administration has still provided no answers as to how it could have gone so horribly wrong.

Most of Europe, however, seems grimly aware that armed conflict with Russia might be inevitable. The calls for Ukraine to become a member of the alliance are growing stronger, and it might end up being a call Biden cannot resist. Russia has all but promised a major reprisal in Europe should NATO invite Ukraine into the fold, but that does not seem to deter the smaller nations closer to Russia’s borders than the U.S.

Ukraine is clearly seeking protection against an aggressive Russia under the leadership of Putin. But Biden’s top concern, though they aren’t his concerns alone, is the risk of armed conflict with a major geopolitical power.