Former US President Donald Trump pledged, in a television interview, to "never withdraw" from the race for the White House despite criminal charges being brought against him, stressing that President Joe Biden is not eligible to run again.

Trump, who faces 34 criminal charges in New York in the case of paying money to buy a pornographic actress's silence, said there was nothing stopping him from running until "conviction".

"I will never quit," he told Fox News anchor Tucker Carlson, stressing, "It's not in my nature. I don't do it."

Trump, 76, in his first major media appearance since appearing in court last week, questioned the ability of the 80-year-old Biden to fight for re-election in 2024.

"I don't see how that is possible," he said, adding, "It's not about age (...) I don't think he's capable of it."

"I don't see Biden being able to do that, either physically or mentally. I don't see that," he continued.

Trump and other senior Republicans regularly question Biden's mental state and apparent weakness.
Right-wing media such as Fox News frequently highlight Biden's slips and moments when Sharda appears to have lost focus.

During Trump's tenure, the "Fox" network was an open platform for the former president to express his views, to the extent that he would appear on its programs without warning and speak at length if he needed to comment on something.

The relationship between the former president and the channel was strained after Trump's defeat by Biden in 2020, but it returned to regain its heat with the intensification of competition for the Republican presidential nomination.

The interview, the second part of which is expected to be broadcast on Wednesday, comes after weeks of text messages circulating in which Carlson speaks disparagingly of Trump after losing the election.

The messages were revealed as part of a $1.6 billion lawsuit filed by Dominion Voting Systems against Rupert Murdoch's Fox News over its coverage of Trump's allegations of fraud in the 2020 election.

"We're so close to being able to ignore Trump most nights. I really can't wait," says one of the text messages Carlson sent two days before the Capitol stormed.

Another message reads, "I hate him so much," but the messages were not addressed during the interview.