- Watch the second US presidential debate LIVE on SBS at 12pm (AEDT) or live streamed .
Four women attended the press conference, streamed live on Facebook, as Trump tries to stamp out the controversy around a leaked tape in which he made lewd remarks about forcing himself on women.
"These four very courageous women have asked to be here," Trump said.
One of the woman, Juanita Broaddrick, claimed that former US President Bill Clinton raped her.
"Mr Trump may have said some bad words but Bill Clinton raped me and Hillary Clinton threatened me," she said at the press conference.
"I don't think there's any comparison."
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.
With the US election less than a month away, Republican lawmakers and governors abandoned Trump in droves, despite a rare televised apology by the candidate, whose sexually aggressive remarks were caught on a live mike in 2005.
Trump himself was defiant, tweeting: "So many self-righteous hypocrites. Watch their poll numbers -- and elections -- go down!"
But even his surrogates went to ground, leaving former New York mayor Rudolf Giuliani as the billionaire's lone defender on Sunday television talk shows.
Trump campaign manager Kellyanne Conway and Republican National Committee chairman Reince Preibus both backed out of scheduled television appearances ahead of the debate in St. Louis, Missouri.
Mike Pence, Trump's running mate, also suspended his campaign appearances after declaring on Saturday that he did not condone and "cannot defend" the Republican standard-bearer.
The scandal -- just the latest involving his treatment of women -- could not come at a worse time for Trump, who has taken a beating in the polls since his sloppy performance in the first presidential debate September 29.
An average of national polls compiled by RealClearPolitics.com has Clinton in the lead by 4.5 percentage points.
National media, meanwhile, have dug up the candidate's past behavior, including agreeing with an interviewer that his daughter Ivanka was a "piece of ass". In a 2002 interview with Howard Stern, Trump also said he preferred leaving women over a certain age.
"What is it at 35? It's called check-out time," he quips.
Source: AFP
Debate with a twist
The two candidates face off starting at 9:00 pm (0100 GMT Monday) at Washington University in St Louis, with the added twist that this time they will take questions from the audience in a town hall-style forum.
"He's as prepared as he's ever been and he's all ready for the debate tonight," Giuliani said on NBC's Meet the Press.
"He obviously, you know, feels very bad about what he's said. He apologized for it, will probably do it again. What he'd like to do is move onto the issues that are facing the American people."
How much the "elephant in the room," as Republican House speaker Paul Ryan referred to the tape on Saturday, dominates the debate is an open question.
Giuliani warned that Trump could well go after Clinton's past marital troubles with her husband Bill, the former president.
"I do believe there's a possibility he'll talk about Hillary Clinton's situation if it gets to that. I don't think he prefers to do that. But I think he will."
Tim Kaine, Clinton's running mate, suggested that while audience members would have questions about Trump's treatment of women, the former secretary of state intended to stick to basic issues like the economy and national security.
"If Donald wants to talk about something other than what voters want to talk about, that's his choice," Kaine said on CNN's State of the Union show. "But I suspect that Hillary Clinton is going to talk about the things that voters really care about."
Clinton may also have to worry about a WikiLeaks disclosure of excerpts from private speeches she gave to major banks in 2013 and 2014.
Although overshadowed by the Trump tape, they show she expressed views in favor of open trade and Wall Street self-regulation to those audiences that are at odds with her positions as a candidate.
John Podesta, a Clinton adviser from whose email account the excerpts were hacked, insisted there were taken out of context.
"They are not diametrically opposed," he said on Fox News Sunday. "Again, you can pull a few words out of context, but what he said on this campaign trail is she'll be tough on Wall Street. That's exactly what she'll do."
Republican breach
Even a winning performance by Trump, however, seems unlikely to mend the deep breach he has opened in the Republican party, alarmed about the scandal's fallout in other down-ballot races.
Notable defectors included Senator John McCain, the 2008 Republican nominee, who said Trump's "demeaning comments about women and his boasts about sexual assaults, make it impossible to continue to offer even conditional support for his candidacy.”
The New York Times reported that by late Saturday 36 Republican members of Congress and governors had disavowed Trump's candidacy.
Some leading Republicans called on Trump to quit the race, but he vowed he would never do that and legal experts said removing him from the top of the ticket would be extremely difficult.
Trump predicted Saturday that the controversy would blow over.
"I think a lot of people underestimate how loyal my supporters are," he told the Times.
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