George Clooney was 'shaken' when Biden failed to recognize him at star studded fundraiser: authors

By the time the 2024 Presidential race had started, Clooney had known Biden "well for fifteen years."

"He had last seen Biden on December 4, 2022, when Clooney was in D.C. with his wife, Amal, to be celebrated at the Kennedy Center Honors," the authors wrote. "Biden looked older, sure, but in the East Room of the White House, at the reception for the honorees, the President was playful and seemed cogent enough."

Fast-forward to 2024, and the authors claim Clooney - who was accompanied by good friend and fellow actor Julia Roberts - immediately noticed Biden's physical decline the moment he saw him. 

"The President appeared severely diminished, as if he'd aged a decade since Clooney last saw him, in December, 2022," they wrote. "He was taking tiny steps, and an aide seemed to be guiding him by the arm."

According to the book, Clooney "felt a knot" form in his stomach as the frail President approached him. 

"Biden looked at him. 'Thank you for being here,' he said. 'Thank you for being here.'"

"'You know George,' the assisting aide told the President, gently reminding him who was in front of him. 'Yeah, yeah,' the President said to one of the most recognizable men in the world, the host of this lucrative fund-raiser. 'Thank you for being here.'"

The authors wrote that it "seemed clear" that Biden "had not recognized Clooney."

"It was not O.K.," an insider, who had witnessed the moment, told the authors, per the excerpt. "That thing, the moment where you recognize someone you know -especially a famous person who's doing a f---ing fundraiser for you - it was delayed. It was uncomfortable."

"Clooney was shaken to his core. The President hadn't recognized him, a man he had known for years. Clooney had expressed concern about Biden's health before-a White House aide had told him a few months before that they were working on getting the President to take longer steps when he walked-but obviously the problem went far beyond his gait. This was much graver."

Biden was showing signs of "obvious brain freezes and clear signs of a mental slide."

"It was, to some of them, terrifying," the authors wrote. 

Representatives for Clooney, Biden, Tapper and Thompson did not immediately respond to Fox News Digital's request for comment. 

"This is about age. Nothing more. But also nothing that can be reversed. We are not going to win in November with this president," the actor wrote. He also stated in the piece that he noticed Biden's frailty during a Hollywood fundraiser for his campaign in June.

"It's devastating to say it, but the Joe Biden I was with three weeks ago at the fund-raiser was not the Joe 'big F-ing deal' Biden of 2010. He wasn't even the Joe Biden of 2020. He was the same man we all witnessed at the debate," Clooney wrote.

"I was raised to tell the truth," Clooney, the son of a journalist, said when asked about the essay on "60 Minutes". "I had seen the president up close for his fundraiser, and I was surprised, and so I feel as if there were a lot of profiles in cowardice in my party through all of that. And I was not proud of that, and I also believed I had to tell the truth."

WATCH: GEORGE CLOONEY ACCUSES MEDIA OF CONCEALING BIDEN'S MENTAL DECLINE