US presidential candidate Donald Trump has apologised for obscene comments about women he made in a newly released videotape from 2005.
Mr Trump said that "these words don't reflect who I am... I apologise".
In the video, Mr Trump says "you can do anything" to women "when you're a star" and brags about trying to grope and kiss women.
Top Republicans condemned the comments. His election rival Hillary Clinton called them "horrific".
"We cannot allow this man to become president," she posted on Twitter.
Warning: The rest of this article contains some graphic language
In the video, Mr Trump is heard saying, "Grab them by the pussy. You can do anything."
"Certainly has been an interesting 24 hours!" Mr Trump wrote on Twitter on Saturday.
Mr Trump's 2005 comments overshadowed the release of transcripts of Mrs Clinton's speeches to private events, by the whistle-blowing site Wikileaks.
What did Mr Trump say?
In the video, posted by the Washington Post, Mr Trump is heard bragging to TV host Billy Bush about trying to have sex with a married woman as well as kissing and groping others.
The clip was part of unaired footage of an Access Hollywood segment ahead of Mr Trump's appearance on the soap opera Days of Our Lives.
"I moved on her and I failed. I'll admit it," Mr Trump is heard saying. "She was married. And I moved on her very heavily.
"I moved on her like a bitch, but I couldn't get there. And she was married. Then all of a sudden I see her, she's now got the big phony tits and everything. She's totally changed her look."
Later in the conversation, he told Mr Bush he was "automatically attracted to beautiful" women and often tried to kiss them.
"I just start kissing them," he said. "I don't even wait. And when you're a star, they let you do it. You can do anything."
What does the candidate say now?
Mr Trump's 90-second statement on Saturday morning appeared to be his first full apology in a campaign laced with controversial remarks.
"I've said and done things I regret," he said. "Anyone who knows me knows these words don't reflect who I am. I said it, I was wrong, and I apologise.
"I've never said I'm a perfect person nor pretended to be someone I'm not. I pledge to be a better man tomorrow."
However, he also tried to deflect the impact by attacking former President Bill Clinton.
"Bill Clinton has actually abused women, and Hillary has bullied, attacked and shamed his victims.
"We'll discuss this in the coming days," he said. "See you at the debate on Sunday."
The second TV debate between Mr Trump and Mrs Clinton will take place on Sunday evening in St Louis.
Mr Trump recently said he would not bring up stories about Bill Clinton's infidelities in the debate, after previously threatening to do so.
The latest opinion polls suggest Mrs Clinton is pulling ahead. Mr Trump will need a good performance at the debate to slow the trend.
Mr Trump has said the latest remarks are "nothing more than a distraction" and "locker-room banter".
How have people responded to the tape?
Top Republicans have been incensed.
House Speaker Paul Ryan said he was "sickened by what I heard today" and rescinded his invitation to Mr Trump to attend the Republican Fall Fest in his home state of Wisconsin this weekend.
Senate Majority Leader Mitch McConnell said the comments were "repugnant," adding that Mr Trump "needs to apologise directly to women and girls everywhere".
Another senior Republican, John McCain, said there were "no excuses for Donald Trump's offensive and demeaning comments".
For his part, Billy Bush said he was "embarrassed" by and "ashamed" of the contents of the video.
"It's no excuse, but this happened 11 years ago. I was younger, less mature, and acted foolishly in playing along. I'm very sorry."
The TV host is the first cousin of former President George W Bush.
Mrs Clinton's campaign released a video featuring the audio, playing over footage of women and girls.
Is this Trump row different? - Katty Kay, Presenter, BBC World News
The day after a video emerged in which he suggested he could have any woman he wants because he's a star and so could just grab them by the pussy, Mr Trump is in a whole ocean of hot political water.
Enough, quite possibly, to sink any chance he had of winning the White House.
There is a violence in the phrases "grab 'em by the pussy" and "you can do anything" that any victim of abuse would recognise and that most women would find sickening.
But this tape doesn't just offend women, judging from the reaction in the Republican party. It has offended a lot of men too. Whether those men will now withdraw their endorsements of him is yet to be seen.