List of Joe Biden's gaffes at NATO summit

US President Joe Biden had a series of verbal slip-ups on Thursday alongside the NATO summit in Washington, an unfortunate development for the 81-year-old as he tries to move past concerns that he is too old to run for re-election.

Verbal gaffes are not unusual in the long political career of Biden, who overcame a childhood stutter, but there is closer attention on him amid the fallout from his dismal debate performance against Republican candidate Donald Trump last month.

Trump, who is 78, and also has faced concerns about his age, frequently made false claims during the debate and often rambles during campaign speeches.

Below is a summary of Biden's mistakes on Thursday.

Biden mistakenly calls Zelenskyy 'Putin'

Biden mistakenly referred to Ukrainian President Volodymyr Zelenskyy as "President Putin".

"And now I want to hand it over to the president of Ukraine, who has as much courage as he has determination, ladies and gentlemen, President Putin," Biden said at the NATO summit, drawing gasps from those in the room.

"Going to beat President Putin, President Zelenskyy. I am so focused on beating Putin," Biden said while correcting himself.

Biden mistakenly refers to Harris as Trump

During a news conference on Thursday evening, Biden mixed up the name of his vice president, Kamala Harris, and his rival Trump.

"Look, I wouldn't have picked Vice President Trump to be vice president if she was not qualified to be president. So start there," Biden said as he responded to a question from Reuters about his confidence in Harris.

Biden fumbles 'chiefs of staff'

Biden also struggled at the news conference to find the words "chiefs of staff," mistakenly referring to the group of the country's top uniformed military leaders as "commander in chief," the title he holds as president.

"And so our military is working on following the advice of my commander in chief my, my, my, the chiefs of staff, of the military as well as the secretary of defense and our intelligence people."