NEW YORK: Republican presidential candidate Donald Trump plunged into a deep crisis on Friday after a bombshell 2005 recording came to light in which he boasted in vulgar terms about trying to have sex with an unidentified married woman and groping women, saying “when you're a star, they let you do it”.

Trump scrambled to prevent his campaign from falling apart early on Saturday with a hastily prepared video statement expressing regret for making lewd comments about women.

"Anyone who knows me knows these words don't reflect who I am. I said it, I was wrong, and I apologise," Trump said in his video statement, posted on his Facebook page.

He declared himself a changed man, but raised the infidelities of former President Bill Clinton and slammed his Democratic opponent, Hillary Clinton, saying he would talk more about their past in coming days.

"This is nothing more than a distraction from the important issues we're facing today," he said, before turning to former President Bill Clinton's infidelities.

In the recorded conversation, Trump was wearing a microphone and chatting on a bus with Billy Bush, then host of NBC's “Access Hollywood” ahead of a segment they were about to tape.

“I did try and f*** her. She was married,” Trump said. “I moved on her like a b***h, but I couldn't get there.” Trump talked about his attraction to beautiful women. “I just start kissing them,” he said.

“And when you're a star they let you do it,” he said. "Grab them...you can do anything."

Trump, who has brought up former President Bill Clinton's infidelities as a criticism of Hillary Clinton, calling her a “total enabler”, responded to the audio.

“Bill Clinton has said far worse to me on the golf course — not even close. I apologise if anyone was offended,” Trump said.

Earlier, in a brief written statement, Trump shrugged off the leaked tape as “locker room banter, a private conversation that took place many years ago”.

“Access Hollywood” confirmed the video in its own report, saying it discovered the comments in its library. Billy Bush said in a statement to Variety he was “embarrassed and ashamed” of his comments.

A stream of Republican leaders denounced the remarks, first published by the Washington Post, which threaten Trump's already shaky standing with women voters just a month ahead of the Nov 8 presidential election.

House of Representatives Speaker Paul Ryan, the top Republican elected official, said he was “sickened” by the comments and said Trump would no longer attend a campaign event in Wisconsin with him on Saturday.

“I hope Mr. Trump treats this situation with the seriousness it deserves and works to demonstrate to the country that he has greater respect for women than this clip suggests,” Ryan said in a statement.

Reince Preibus, chairman of the Republican National Committee, said: “No woman should ever be described in these terms or talked about in this manner. Ever.”

Senate Majority Leader Mitch McConnell said the comments were “repugnant” and that Trump “needs to apologise directly to women and girls everywhere.”

US Representative Jason Chaffetz of Utah, who has been one of Clinton's fiercest critics, said he had retracted his endorsement of Trump, telling CNN he would not be able to look his 15-year-old daughter in the eye if he voted for Trump.

Utah's Republican Governor Gary Herbert said on Twitter he would also no longer vote for Trump.

“Tonight, millions of Republicans are facing a moment of truth,” Herbert said.

Republican lawmaker Mike Coffman from Colorado told CBS that Trump should “step aside” and said “his defeat at this point seems almost certain”.

Other prominent Republicans also condemned the comments but stopped short of withdrawing their support for their candidate, including Arizona Senator John McCain and Texas Senator Ted Cruz.

New ground

Trump, known for his unconventional and controversial speaking style, has made a series of gaffes in his campaign, but the “graphic nature” of the clip will hurt his standing among women, independents, and wavering Republicans, said David Yepsen, director of the Paul Simon Public Policy Institute at Southern Illinois University.

“We've never seen something like this Trump clip in a modern presidential campaign,” Yepsen said, calling the incident “sad for the American political system” and for Trump's supporters.

Republican strategist Ron Bonjean said “this feels like it is quickly becoming a political 'game over'” for Trump.

“Unless voters don't care about these issues or believe that this is simply political dirty tricks by releasing the videos now, Trump is going to have to pull a rabbit out of his hat in order to turn things around,” Bonjean said.

Still, Trump's past controversial comments have failed to shake his core supporters, said David Axelrod, a former political adviser to Democratic President Barack Obama.

“Appalling as the (Trump) tape is, I'm reminded of all the times we have said, THIS time he's REALLY done,” Axelrod said on Twitter.

The revelation comes right before Sunday's town hall-style debate, seen as critical as Trump tries to rebound from a dip in some opinion polls after a rocky performance in the first debate.

Clinton, who slammed Trump's comments as “horrific”, was also hit by a leak on Friday. Wikileaks published what appeared to be excerpts of her paid speeches to corporations, the transcripts of which the campaign has refused to release.

The excerpts were likely to provide Trump some fodder for attacking Clinton in the debate. In them, she voices support for open trade and borders and discusses taking different positions in public and in private.

However, Yepsen said the excerpts would likely be eclipsed by Trump's clip. “The two things aren't comparable,” he said.

The US government formally accused Russia on Friday of hacking Democratic Party organisations ahead of the presidential election. Wikileaks has declined to name its sources.

A spokesman for the Clinton campaign declined to confirm whether the Wikileaks emails were authentic and noted that other hacked documents have been faked.