“US President Joe Biden stated that he decided not to seek re-election because he was concerned that the internal party conflict over his candidacy would be a significant distraction for Democrats. He emphasized that his primary goal was to defeat Donald Trump in November.”

In his first interview since dropping out of the race, Mr. Biden, 81, stated that he had “no serious problem” with his health. He attributed his poor debate performance to being unwell at the time and dismissed worries about his age and mental sharpness.

The US president pledged to support Kamala Harris by doing whatever his vice-president “thinks I can do to help most.”

“We must, we must, we must defeat Trump,” he told US broadcaster CBS News.

Mr. Biden said that if he had continued his campaign, the presidential contest would have gone “down to the wire.”

“A number of my Democratic colleagues in the House and Senate thought that I was going to hurt them in the races,” he said.

“And I was concerned if I stayed in the race, that would be the topic. You’d be interviewing me about, Why did Nancy Pelosi say, why did so — and I thought it’d be a real distraction.”

Former House speaker Nancy Pelosi was widely reported to have led the push to oust Mr Biden – a claim she has not exactly denied – after his halting debate performance against Trump on 27 June.

In the pre-recorded interview broadcast on Sunday, Mr. Biden misspoke several times, but overall, he seemed more coherent than during the live televised debate. He attributed his poor debate performance to illness. Previously, he has also mentioned jet lag and lack of rest as contributing factors.

As pressure continued to ratchet up, he announced his exit from the race on 21 July.

A potential battle to replace him at the top of the Democratic ticket never materialised and party support swiftly coalesced around Vice-President Harris, who has so far outperformed Mr Biden in opinion polls.

The president has said he intended to be a bridge to the next generation when he ran for the White House in 2020.

“When I ran the first time, I thought of myself as being a transition president. I can’t even say how old I am. It’s hard for me to get it out of my mouth.”