Washington: President Donald Trump threatened former vice-president Joe Biden on Thursday, saying in a tweet that Biden "would go down fast and hard" if the two men ever physically fought. Trump was responding to Biden's comments Tuesday about how, if he was in high school, Biden would "beat the hell" out of Trump for disrespecting women.

Biden, speaking at a University of Miami rally to combat sexual assault, said, "A guy who ended up becoming our national leader said, 'I can grab a woman anywhere and she likes it,'" referring to an Access Hollywood audio recording in which Trump is heard boasting about kissing and groping women without their consent.

Biden said when he was asked if he would like to debate Trump, "If we were in high school, I'd take him behind the gym and beat the hell out of him."

The back-and-forth blustering between two men in their 70s comes a day after Trump criticised two of his predecessors, presidents Barack Obama and George W. Bush, for not being able to improve relations with Russia.

And Trump is facing revived sexual misconduct accusations after a New York state judge ruled that a defamation lawsuit from a woman who has said Trump made unwanted sexual advances could go forward.