Washington - Lance Armstrong "came clean" to Oprah Winfrey on his use of banned drugs, the talk show host said on Tuesday, as anticipation built for the telecast of her interview with the shamed cyclist.
Winfrey told "CBS This Morning" that her OWN cable network will broadcast the two-and-a-half-hour interview unedited over two nights from Thursday. Originally, a shorter broadcast was planned for one night only.
"I didn't get all the questions asked, but I think the most important questions and the answers that people around the world have been waiting to hear were answered," Winfrey said.
"I would say he did not come clean in the manner that I expected," she added. "It was surprising to me. I would say that for myself, my team, all of us in the room, we were mesmerised and riveted by some of his answers."
But even before Armstrong's mea culpa had been seen, critics were questioning his choice of forum, saying an interview with Winfrey lacked the rigor of testimony under oath before anti-doping authorities.
"While WADA encourages all athletes to come clean about any doping activities they have been involved with or know about, these details must be passed on to the relevant anti-doping authorities," said David Howman, director general of the World Anti-Doping Agency.
The Swiss-based International Cycling Union also called for Armstrong to give evidence to its ongoing investigation into widespread doping in the sport it governs.
Legal analysts meanwhile said that the US government could potentially prosecute Armstrong for fraud related to his receiving government sponsorship while riding for the US Postal team from 1998-2004.
"Because he has now admitted he doped, that makes it a lot easier to prove a fraud claim," sports lawyer Brian Socolow said.
The interview was Armstrong's first since he was stripped of his record seven Tour de France titles after the US Anti-Doping Agency, in a 1,000-page report, put him at the heart of the greatest sports doping scandal in history.
For a decade, he had vigorously denied using banned substances to win his way into the history books after battling cancer.
Prior to sitting down with Winfrey on Monday in his hometown of Austin, Texas, the 41-year-old went to the offices of the Livestrong cancer charity he founded and apologised in person to its staff.
Livestrong spokeswoman Rae Bazzarre said Armstrong's apology was "sincere and heartfelt."
Asked if Armstrong had "come clean" to her, Winfrey said she and Armstrong had agreed at the outset not to talk about the content of the interview.
But a source with knowledge of the interview confirmed that the Texan admitted to Winfrey using banned substances in his career.
Winfrey, speaking from Chicago, said she was mystified as to how the content had leaked.
The 58-year-old star said she asked 112 questions in "the biggest interview I've ever done" and grilled Armstrong so intensely that, during a break at the 100-minute mark, Armstrong asked if their conversation might lighten up.
With a world-class scoop on her hands, Winfrey flew home to Chicago with the video tape in her handbag for fear it might be pirated or leaked if beamed back to the editing room via satellite.
Betsy Andreu, the wife of Armstrong's former team-mate Frankie Andreu, has long claimed that she heard Armstrong admit to doping at a 1996 appointment with doctors treating his testicular cancer.
She told ESPN that she didn't know if she'd be able to watch the interview.
A TV confession now, Andreu said, could only be a first step if Armstrong is to repair his reputation in a meaningful way.
"If he really wants a second chance, then he's going to have to tell the truth of everything and stop protecting people, especially the people who helped him get away with it," she said.