Former United States President Joe Biden has said he would not have pursued a second presidential term if he had known about his cancer diagnosis while seeking re-election in 2024.

Biden made the revelation in an interview with PEOPLE magazine ahead of the release of his upcoming presidential memoir, Promise Me, America, where he reflected on his decision to withdraw from the presidential race and the controversy surrounding his health.

The former president also downplayed the significance of his widely criticised June 2024 debate performance against then-Republican presidential candidate Donald Trump, during which he struggled to articulate his positions and appeared visibly fatigued.

The debate triggered widespread concerns among Democrats about his fitness to continue in the race, eventually contributing to his decision to withdraw and endorse his then-Vice President, Kamala Harris, just 107 days before the election.

However, Biden dismissed suggestions that the debate performance had significantly affected his political fortunes.

"Look, I don't know anybody who hasn't made a mistake in a debate. To me, it was not very consequential. First of all, I thought there'd be another debate, which there wasn't. But notwithstanding the fact that there wasn't another debate, it didn't disturb me because it wasn't consequential," he said.

Four months after leaving the White House, Biden was diagnosed with an aggressive form of prostate cancer.

Reflecting on the diagnosis, the former president acknowledged that he had experienced periods of feeling unwell before his condition was discovered but insisted that he had no knowledge of the illness while pursuing re-election.

He said knowing about the cancer at the time would have fundamentally changed his decision to remain in the presidential race.

"If I had known that I was feeling lousy because I had cancer, I would have resigned. I would've not gone forward, because I don't think an 80-year-old man with cancer should be running for (president)," Biden said.

He, however, maintained that he believed he was the most qualified person to continue leading the country at the time.

"But that wasn't the case … I believe that on an objective basis, I was the best-equipped person to do the job," he added.

Biden also rejected suggestions that his administration deliberately concealed information about his health while he was in office.

According to him, his team made the cancer diagnosis public promptly after receiving confirmation of his condition.

He further stressed the importance of transparency about the health challenges of national leaders, noting that openness could help normalise medical conditions also experienced by ordinary citizens.

His forthcoming memoir, *Promise Me, America*, is scheduled for release next Tuesday. However, Biden disclosed that his ongoing cancer treatment would limit his ability to participate in extensive promotional activities surrounding the book.

The revelations offer further insight into Biden's final months in office, his controversial 2024 re-election bid and the health challenges that emerged after his departure from the White House.