Lance Armstrong has confessed to using performance-enhancing drugs during all seven of his Tour de France victories, saying: "I view this situation as one big lie."
After years of denials, the 41-year-old American told Oprah Winfrey that during his record run, from 1999 to 2005, he used blood-boosting agent EPO, blood doping, testosterone, cortisone and human growth hormone.
Armstrong, who was last October stripped of all results dating from 1 August 1998 and banned from sport for life, denied doping during his comeback from retirement in 2009, when he finished third in the Tour, and 2010 and refuted suggestions he paid off cycling's world governing body, the UCI, to cover up a positive test in 2001.
In hindsight he wishes he had co-operated with the United States Anti-Doping Agency investigation which proved his downfall.
"This story was so perfect for so long," Armstrong, who confirmed his doping in a series of answers to yes-no questions, told Oprah.
"I try to take myself out of this situation and look at it: you overcome the disease, you win the Tour de France seven times, you have a happy marriage, you have children.
"It's this mythic, perfect story and it wasn't true."
Asked if it was hard to live up to that image, Armstrong said: "Impossible. The story is so bad and so toxic, a lot of it's true."
In the interview with talk-show host Winfrey, recorded on Monday in his home city of Austin, Texas, Armstrong was asked why he chose to confess his misdemeanours now.
"I don't know that I have a great answer," he said.
"This is too late. It's too late for probably most people and that's my fault.
"I view this situation as one big lie, that I repeated a lot of times. It wasn't as if I just said no and I moved on.
"While I've lived through this process, especially the last two years, one year, six months, two, three months, I know the truth, the truth isn't what was out there. The truth isn't what I said."
Asked whether he felt it was possible to win the Tour seven times in succession without doping, Armstrong said: "Not in my opinion."
Armstrong's drug use began in the "mid-90s", he said.
"I suppose earlier in my career there was cortisone and then the EPO generation began," said Armstrong, who won the world road race title aged 21 in 1993.
"I didn't invent the culture, but I didn't try to stop the culture. The sport is now paying the price because of that."
Following the broadcast of the interview, the United States Anti-Doping Agency (USADA) chief executive Travis Tygart said in a statement: "Tonight, Lance Armstrong finally acknowledged that his cycling career was built on a powerful combination of doping and deceit.
"His admission that he doped throughout his career is a small step in the right direction. But if he is sincere in his desire to correct his past mistakes, he will testify under oath about the full extent of his doping activities."