US election: Trump camp goes on attack ahead of debate

Donald Trump has appeared alongside a panel of women just hours ahead of today's crucial second US presidential debate, with one of them accusing Bill Clinton of raping her.

The explosive claims were made by Juanita Broaddrick, a nursing home administrator who came forward after the Monica Lewinsky scandal and alleged Bill Clinton had raped her in the seventies.

"Bill Clinton raped me, and Hillary Clinton threatened me," said Broaddrick.

Four women attended the press conference, where former president Clinton was accused of rape and unwanted advances.

"These four very courageous women have asked to be here," Trump said.

Trump had threatened to talk about Bill Clinton's past infidelities during the debate and has stepped up the attacks against the former president since a 2005 video emerged of the Republican candidate making vulgar comments about women.

Trump has remained defiant in the face of calls for him to abandon the US presidential race, while attacking prominent Republicans and saying he has "tremendous support" despite a storm over his vulgar comments about women.

The debate in St Louis, Missouri will start at 1200 Monday AEDT.