NATO leaders pledged enduring support for Ukraine and commitment to their alliance as they wrapped up a three-day summit overshadowed by doubts over President Joe Biden’s fitness to run crucial power the United States.

The 32-nation alliance used the pomp-filled 75th anniversary gala in the US capital to showcase its resolve against Russia two and half years into the Kremlin’s invasion of its pro-Western neighbour.

But the gathering was clouded by uncertainty in the United States as Biden fights for his political survival.

“I will not walk away from Ukraine. I will keep NATO strong,” Biden said in his closing press conference. “That’s exactly what we did, and exactly what we’ll continue to do now.”

The US leader compared his commitment to the trans-Atlantic alliance to comments from his challenger, former president Donald Trump.

“My predecessor has made it clear he has no commitment to NATO. He’s made it clear that he would feel no obligation to honor Article 5,” Biden said, referring to the alliance’s commitment of common defense.

Biden met Ukraine’s President Volodymyr Zelensky along with other NATO leaders on the third — and final — day of the summit after pledging new air defenses to help protect the war-torn country.