Donald Trump has insisted that Joe Biden would “go down fast and hard, crying all the way” after the Democrat threatened to “beat the hell out of” the US president if they were at school.

Mr Biden, the former US vice-president, said earlier this week that he would have taken Mr Trump “behind the gym” and beaten him up over his crude comments about women.

The 75-year-old spoke at an anti-sexual assault rally in Florida on Tuesday and cited lewd comments Mr Trump made in a 2005 “Access Hollywood” tape about grabbing women.

Mr Biden reportedly said: “If we were in high school, I’d take him behind the gym and beat the hell out of him.”

But Mr Trump lashed out at Mr Biden in a tweet on Thursday, saying he “would go down fast and hard, crying all the way.”

Saying “Don’t threaten people Joe!”, he said Mr Biden is “trying to act like a tough guy”, but “actually, he is weak, both mentally and physically, and yet he threatens me, for the second time, with physical assault”.

In his comments earlier this week, Mr Biden said: “When a guy who ended up becoming our national leader said, ‘I can grab a woman anywhere and she likes it’ and then said, ‘I made a mistake.

“They asked me would I like to debate this gentleman, and I said no. I said, ‘If we were in high school, I’d take him behind the gym and beat the hell out of him.”

Biden was referring to the Access Holiday video that emerged in 2016 in which Mr Trump was heard making lewd comments about women.

Mr Trump later took the rare step of apologising for what he described as “locker room talk”.

Mr Biden said: “I’ve been in a lot of locker rooms my whole life. I’m a pretty damn good athlete.”

He added: “Any guy that talked that way was usually the fattest… in the room.”

He was speaking at a rally for his “It’s On Us” advocacy group that aims to target sexual assaults on college campuses.