Former US president Donald Trump, having been criminally charged in New York, pledged Tuesday to "never drop out" of the 2024 race for the White House, and insisted Joe Biden is not fit to run again. The Republican real estate magnate, who is facing 34 felony counts in New York over alleged hush money paid to an adult film actress, told Fox News anchor Tucker Carlson that nothing would prevent him from running -- even a conviction. "I'd never drop out," he said. "It's not my thing. I wouldn't do it." Trump, 76, in his first major interview since being arrested and fingerprinted last week, cast doubt on whether Democrat Biden, 80, would be in the 2024 race. "I don't see how it's possible," he said. "It's not an age thing... I don't think he can. "I just don't see Biden doing it from a physical or a mental standpoint. I don't see it." Trump and other senior Republicans have repeatedly cast doubt on Biden's mental acuity and apparent frailty. Right wing outlets like Fox News frequently highlight his verbal flubs, and moments where he appears to have lost his train of thought. Throughout his own presidency, Fox offered an uncritical forum for Trump to air his grievances, with the then-commander-in-chief sometimes calling in unannounced to shows and talking at length to presenters. The relationship cooled after Trump's defeat to Biden at the ballot box in 2020, but has steadily grown again as the Republican nominating contest heats up. Part two of the interview is expected to be broadcast on Wednesday.