Washington DC - A Democratic senator on Wednesday called on President Joe Biden to ditch his reelection bid, capping a brutal day that saw mounting pressure from George Clooney and party heavyweight Nancy Pelosi.

As the 81-year-old tried to show his leadership credentials at a NATO summit in Washington, domestic calls have been growing for Biden to quit following his disastrous debate performance against Republican challenger Donald Trump.

At least eight House Democrats have openly called on Biden to not seek reelection, but Peter Welch of Vermont became the first in the Senate to explicitly do so as concerns rise over his age and fitness.

"For the good of the country, I'm calling on President Biden to withdraw from the race," he said in an opinion piece in the Washington Post.

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Axios reported Wednesday that Senate Majority Leader Chuck Schumer had also privately signaled to donors that he was open to replacing Biden on the Democratic ticket.

However, in a statement shared by his office Wednesday evening, Schumer said "I support President Biden and remain committed to ensuring Donald Trump is defeated in November."

Biden has been trying to stem a growing tide of Democrats saying that he cannot win in November, but a steady drip of public revolt and doubt is squashing efforts to turn the page on the crisis.

After former House speaker Nancy Pelosi expressed some ambiguity on Wednesday, Hollywood star Clooney penned a damaging op-ed in the New York Times, just three weeks after co-hosting a huge fundraiser in Los Angeles that raised nearly $30 million for Biden.

"It's devastating to say it, but the Joe Biden I was with three weeks ago at the fundraiser was not the Joe 'big F-ing deal' Biden of 2010," Clooney wrote.

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"He wasn't even the Joe Biden of 2020. He was the same man we all witnessed at the debate."

In response to Clooney's editorial, the Biden campaign pointed to the president's statements on Monday saying he was committed to running again in November.

Biden has blamed jet lag and a cold for his performance in the June 27 television debate with Trump.

Media-shy for much of his presidency, he will also give a fresh interview to NBC on Monday as he seeks to convince voters and party members.