By Vicky Wong and Sarah Smith, North America editor, From BBC

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Joe Biden’s press conference in which he insisted he was still fit to run for US president has failed to silence critics from his own party.

Three Democratic politicians joined the growing list calling on Mr Biden to drop out of the US presidential race.

Calls for the 81-year-old to step aside have escalated since he stumbled through a TV debate with Republican Donald Trump last month.

At an hour-long briefing taking reporters’ questions on Thursday night he was more steady and fluent but there were also gaffes.

He mistakenly referred to his deputy, Kamala Harris, as “Vice President Trump” when answering the first question.

Two hours earlier at a Nato event he introduced Ukraine’s leader Volodymyr Zelensky as “President Putin” before correcting himself.

It means Mr Biden’s candidacy still remains in peril, with the possibility of more defections over the next few days.

Some donors including Hollywood actor George Clooney have pulled their financial support, saying he is not competent to carry out another four-year term.

One Democratic fundraiser who wants Mr Biden to step down told the BBC that like-minded Biden sceptics felt the president had done OK at the news conference, but not well enough to change minds.

A problem for Mr Biden going forward is that he will be under constant and intense scrutiny at every event. 

Any slip or mistake will be seized on as evidence that he is neither fit nor capable enough to be running for a second term.

Shortly after he finished his press conference, Connecticut congressman Jim Himes posted on X praising Mr Biden’s record in public service, but calling on him to step away from the campaign.

The strongest candidate to confront the “threat” posed by Trump, he wrote, was no longer Joe Biden.

Illinois congressman Eric Sorensen also posted on social media that Mr Biden ran in 2020 “with the purpose of putting country over party. Today I am asking him to do that again”.

• Biden defiant but gaffes undermine fightback

California congressman Scott Peters was the third to speak out, saying the “stakes are high, and we are losing course”.

They bring the tally of Democratic politicians calling on Mr Biden to end his candidacy to 19.

During the briefing, Biden insisted to reporters that he’s in the race to “complete the job”.

“If I slow down and can’t get the job done, that’s a sign I shouldn’t be doing it,” he said. “But there’s no indication of that yet.”

Many of his supporters in Congress came out immediately after the news conference to echo his belief that he is the best candidate.

“We’ve got to stop the nitpicking and then focus on the work ahead. This guy has done it, he’s done it in the past,” said Democratic National Committee chairman Jaime Harrison.

US allies also weighed in on Mr Biden’s side, with UK Prime Minister Keir Starmer saying he had been in “very good form” when they met face-to-face at the summit.

French president Emmanuel Macron called the mistakes just a slip of the tongue, saying that Mr Biden was on top of matters.

But Trump was quick to mock Mr Biden for his Kamala Harris mistake. “Great job, Joe!” he wrote on Truth Social.

More on US election

• POLICIES: Where Biden and Trump stand on key issues
• GLOBAL: What Moscow and Beijing think of rematch
• ANALYSIS: Could US economy be doing too well?
• EXPLAINER: RFK Jr and others running for president
• VOTERS: US workers in debt to buy groceries

For more on this story go to: BBC