President Joe Biden mistakenly introduced Ukrainian President Volodymyr Zelenskyy as “President Putin” at the NATO summit Thursday, an embarrassing verbal stumble at a time when Biden faces intense questions about his mental competency.

Biden’s confusion of Zelenskyy with the name of the Russian leader who has waged a devastating war on Ukraine for more than two years came less than an hour before Biden was due to face reporters in Washington, D.C., at his first news conference since his tongue-tied, sluggish debate against former President Donald Trump in late June.

It also comes as a growing number of Democrats are calling on Biden to drop out as the party’s presidential nominee.

“And now I want to hand it over to the President of Ukraine, who has as much courage as he has determination,” Biden said at the NATO event in Washington, D.C.

“Ladies and gentlemen — President Putin. President Putin,” Biden said, before catching his mistake.

“He’s gonna beat President Putin, President Zelenskyy,” Biden then said.

Zelenskyy deftly handled the flubbed introduction, quipping, “I’m better.”

Biden replied, “You are a hell of a lot better.”

Biden has suffered from stuttering for decades.

But his recent debate with Trump, and other verbal miscues and moments of apparent confusion have raised concerns that the 81-year-old, who is the oldest sitting U.S. president ever, is exhibiting diminished verbal and mental acuity.

The Biden campaign later Thursday tweeted out a video clip of his gaffe.

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