US President Joe Biden has, for nearly a year, led a coalition united in defense of Ukraine. He has heard Russian leaders accuse him of trying to expand the war. This week, he saw President Vladimir Putin pull out of a major nuclear arms deal. However, he says the US remains committed to defending "every inch of NATO."

Biden was in Warsaw on Wednesday for meetings with leaders of NATO's eastern flank, including Poland, Romania and Lithuania. The allies are dealing with a new security threat after Russian lawmakers suspended their last remaining nuclear treaty with the US.

Biden called the decision to suspend participation in the New START treaty "a big mistake."

He credited the NATO allies in eastern Europe with helping Ukraine beat back Russian forces.

Biden said, "You are on the front lines of our collective defense. And you know better than anyone what is at stake in this conflict."

Romanian President Klaus Iohannis said, "To make sure that this brutal war against Ukraine is Russia's final act, we also must be resolute in deterring further aggression."

Biden has not yet responded to requests to provide the Baltic nations with more NATO air-defense systems. However, he reiterated the importance of maintaining a strong and unified Europe.

Putin has previously called NATO "an existential threat." A Kremlin spokesperson said on Wednesday that the West's reaction to the suspension of the nuclear treaty shows a lack of "willingness for dialogue."