Joe Biden batted away questions about his fitness for office in a highly-anticipated press conference, saying he is the most qualified person to run for United States president, after mistakenly referring to the Ukrainian leader as "President Putin" and his rival Donald Trump as his "vice-president".
Biden addressed reporters on a wide range of topics on the sidelines of the NATO summit in Washington DC, in what was billed as a high-stakes news conference on Friday morning (AEST).
Biden and his supporters hoped his performance would ease .
When asked whether he had any concerns about vice-president Kamala Harris' ability to beat Donald Trump if she ran for the top job, Biden said: "I wouldn't have picked Vice-President Trump to be vice-president if I didn't think she was qualified to be president".
"I think I am the most qualified person to run for president. I beat him once and I will beat him again," he added.
Later, when asked about the "Vice-President Trump" gaffe reportedly being used by Republican nominee Donald Trump to mock Biden's age and memory, Biden retorted sarcastically: "Listen to him".
In other key moments from Biden's first formal solo news conference since November 2023 — described jokingly by White House press staff as his 'big boy press conference':
On the prospect of Kamala Harris becoming president, Biden said he would not have picked her unless he thought she was qualified. "She is qualified to be president. That's why I picked her," he said.
On his mental acuity: Biden said he had taken three "significant and intense" neurological exams. "They say I'm in good shape."
"I'm tested every single day about my neurological capacity to the decisions I make, every day," he added.
On his record on the : Biden insisted he had tried to get aid into Gaza, adding that "Israel occasionally was less than cooperative." He said there should be "no Israeli occupation of Gaza" once the war ends.
Biden refers to Zelenskyy as 'President Putin'
Earlier, Biden had to correct himself after referring to Russian President Vladimir Putin while introducing Ukrainian Volodymr Zelenskyy to the podium, in a gaffe that drew gasps from the audience in the media room.
"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, referring to Zelenskyy, before realising his error and correcting himself.
Ukrainian President Volodymyr Zelenskyy laughs after being mistakenly introduced as "President Putin" by US President Joe Biden during the NATO Summit in Washington. Source: AAP / Will Oliver/EPA
During the press conference later, Biden deflected questions about the gaffe, pointing to the success of the NATO summit.
"Find me a world leader who didn't think it was," he said.
More Democrats call for Biden to drop out
Biden is facing calls by members of his party to drop out of the race ahead of this year's presidential election.
Following his press conference, Democrat Jim Himes called on Biden to "step away" from the race in a statement
"The 2024 election will define the future of American democracy, and we must put forth the strongest candidate possible to confront the threat posed by Trump's promised MAGA authoritarianism," Himes said, according to NBC News.
"I no longer believe that is Joe Biden, and I hope that, as he has through a lifetime of public service, he will continue to put our nation first and, as he promised, make way for a new generation of leaders."
Earlier, Peter Welch became the first Democratic US senator to call on Biden to step aside, joining of the House of Representatives who have appealed to the president to withdraw from the race.
Welch, a first-term senator from Vermont, said Biden should end his candidacy "for the good of the country".
On Friday, Australian Prime Minister Anthony Albanese said that Biden calling Zelenskyy "President Putin" was "unfortunate" but steered clear on whether the US president should step aside from the race.
Albanese said that he sympathised with the mistake.
"Everyone from time to time, I think, has made a slip — it clearly was on his mind who President Zelenskyy is fighting," Albanese told Brisbane radio station 4BC.
A Reuters/Ipsos poll released last week found Biden and Trump tied at 40 per cent each. Other opinion polls have found Trump widening his lead over Biden.