United States President Joe Biden will Thursday give his first press conference since his debate disaster against Donald Trump, in a pressure-cooker moment that could seal the fate of his reelection bid.

The eyes of the world will be on the 81-year-old at a NATO summit as he tries to calm growing calls from his Democratic party to step aside over his age and health.

The White House has dubbed it a “big boy” press conference, and Biden will be under severe pressure to show he can handle what has become a rare unscripted moment in his presidency.

Any missteps by Biden at the 5.30 pm (2130 GMT) event at a Washington DC conference center could turn the trickle of Democrats who have so far urged him to abandon his 2024 election bid into a flood.

The walls closed in further on Wednesday when Hollywood actor and supporter George Clooney called on Biden not to stand, just weeks after holding a glitzy fundraiser for the president.

Party heavyweight and former House speaker Nancy Pelosi also subtly twisted the knife by stopping short of backing Biden, saying only that he should make a decision after the NATO summit.

The first Democratic senator, Peter Welch of Vermont, meanwhile joined at least eight House Democrats in openly urging the man who beat Trump in 2020 not to stand again.

But many Democrats are believed to be waiting to see if Biden pulls off his first solo press conference since November 2023, or whether it will be a repeat of the debate.

Biden has given fewer news conferences than his predecessors. His recent appearances have been joint appearances with foreign leaders restricted to two questions each.

Coupled with a lack of interviews, it has led critics to accuse the White House of shielding the effects of age on America’s oldest president from the public.

* ‘Devastating’ –

White House Press Secretary Karine Jean-Pierre has repeatedly promised Thursday’s “big boy press conference” — a phrase first used by a journalist that she has since adopted — will feature multiple questions.

A poor performance will pour fuel on the flames of the concerns about Biden’s age and health that were sparked when he appeared listless and often incoherent against Republican Trump, 78.

NATO allies have also been seeking reassurance about Biden’s leadership abilities, and over fears that a return of the isolationist Trump could spell trouble for the alliance.

Biden has blamed his debate meltdown on a bad cold and jet lag after two weeks of grueling foreign travel.

But Clooney said in a coruscating New York Times piece on Wednesday that the signs were already there at a June 15 fundraiser in Los Angeles that he co-hosted with actor Julia Roberts.

“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,” wrote Clooney.

“He wasn’t even the Joe Biden of 2020. He was the same man we all witnessed at the debate.”

Clooney said that Biden would lose the presidential election, and Democrats would also lose both chambers of Congress.

Biden has insisted that he is committed to running in November, and with the Democratic party primary votes under his belt there is no real way of forcing him out.

But the New York Times reported on Wednesday that some Democratic grandees like Pelosi are trying a different tack — appealing to his rational side rather than inflaming the stubbornness that has driven his political career.

Vice President Kamala Harris is widely seen to be the frontrunner to replace Biden if he steps aside, but any move would have to be before the Democratic convention in Chicago in August.