Lance Armstrong has admitted using performance-enhancing drugs during all seven of his Tour de France wins.
The 41-year-old made the admission during an interview with Oprah Winfrey.
"I view this situation as one big lie I repeated a lot of times," he said. "I made those decisions, they were my mistake and I'm here to say sorry."
However the cyclist denied it was "sport's biggest doping programme", saying "it was smart, but it was conservative, risk averse".
After years of denials, Armstrong told Winfrey:
Armstrong was stripped of his Tour de France titles last year after being labelled a "serial cheat" by the US Anti-Doping Agency (Usada).
The body said he led "the most sophisticated, professionalised and successful doping programme sport has ever seen".
The American decided not to contest the charges, saying last year he was tired of fighting the allegations. He had always strongly denied doping.
That all changed within seconds of an explosive opening to the interview when Winfrey demanded yes or no answers.
"Did you ever take banned substances to enhance cycling performance?"
"Was one of those substances EPO?"
"Did you use any other banned substances?"
Armstrong admitted to taking performance-enhancing drugs Erythropoietin (EPO), testosterone, cortisone and human growth hormones as well as having blood transfusions.
He continued: "All the fault and blame is on me and a lot of that is momentum and I lost myself in all that. I couldn't handle it. The story is so bad and toxic and a lot of it is true."
Asked if doping was part of the process required to win the Tour, he said: "That's like saying we have to have air in our tyres or water in our bottles. It was part of the job.
"I don't want to make any excuses, but that was my view and I made those decisions."
In a key exchange Winfrey asked: "Did it feel wrong?
Armstrong replied: "No. Scary."
"Did you feel bad?"
"No. Even scarier."
"Did you feel that you were cheating?"
"No. The scariest."
Armstrong continued: "The definition of a cheat is to gain an advantage on a rival or foe. I didn't view it that way. I viewed it as a level playing field. I didn't understand the magnitude of that. The important thing is that I'm beginning to understand it.
"I see the anger in people, betrayal. It's all there. People who believed in me and supported me and they have every right to feel betrayed and it's my fault and I'll spend the rest of my life trying to earn back trust and apologise to people."
On whether it was the biggest doping programme in sport he said: "I didn't have access to anything that anybody else didn't.
"Winning races mattered for me but to say that programme was bigger than the East German doping programme of 70s and 80s is wrong."
Armstrong said his battle with cancer in the mid-1990s turned him into a "fighter".
"Before my diagnosis I was a competitor but not a fierce competitor," he said. "I took that ruthless win-at-all-costs attitude into cycling which was bad."
Armstrong denied riders had to comply to a doping programme to compete for the team, but admitted his personality could imply that.
He said: "Yes, I was a bully. I was a bully in the sense that I tried to control the narrative and if I didn't like what someone said I turned on them.
"We felt like we had our backs against the wall and I was a fighter."
Armstrong said he had not been afraid of getting caught. "Testing has evolved. Back then they didn't come to your house and there was no testing out of competition and for most of my career there wasn't that much out-of-competition testing so you're not going to get caught because you clean up for the races.
"I didn't fail a test. Retrospectively, I failed one. The hundreds of tests I took I passed them."
However, he did admit that he received a back-dated therapeutic user exemption certificate for a cream containing steroids at the 1999 Tour to ensure he did not test positive.
Armstrong retired from cycling in 2005 but returned to the sport between 2009 and 2012.
He told Winfrey that he did not use drugs after his return to the sport. "That's the only thing in that whole Usada report that really upset me," he said.
Armstrong said he regretted his return, and was asked if he would have "got away with it" if he had not come back.
"Impossible to say," he replied, but added his "chances would have been better".
However, he conceded that when he discovered George Hincapie, who was the only man to ride in the same team as Armstrong for each of his seven Tour wins, had given evidence against him last year, he knew his "fate was sealed".
"George is the most credible voice in all of this," Armstrong added. "He did all seven Tours. We're still great friends. I don't fault George Hincapie, but George knows this story better than anybody."
Armstrong said he would now co-operate with Usada. " I love cycling and I say that knowing that people see me as someone who disrespected the sport, the colour yellow," he said.
"If there was a truth and reconciliation commission - and I can't call for that - and I'm invited I'll be first man through the door."
He went on to say that he wished he had complied with the Usada investigation. "I'd do anything to go back to that day," he said.
"I wouldn't fight, I wouldn't sue them, I'd listen. I'd do a couple of things first.
"I'd say give me three days. Let me call my family, my mother, sponsors, [the Lance Armstrong Livestrong] foundation and I wish I could do that but I can't."
Asked if his former doctor Michele Ferrari, who was banned for life by Usada after being found guilty of numerous anti-doping violations, was the "mastermind", Armstrong said: "No. I'm not comfortable talking about other people.
"I viewed Dr Michele Ferrari as a good man and I still do."
He said he regretted "going on the attack" against masseuse Emma O'Reilly, who was an early whistleblower.
"She is one of these people that I have to apologise to," he said. "She's one of these people who got run over, got bullied."
He denied making a $100,000 donation in 2005 to cycling's governing body, the UCI, to cover up a failed drugs test. "It was not in exchange for help," he said. "They called. They didn't have a lot of money. I did. They asked if I would make a donation so I did.
"That story [of a cover up] isn't true. There was no positive test. There was no paying off of the lab. There was no secret meeting with the lab director. I'm no fan of the UCI. That did not happen."
However, Armstrong refused to answer questions regarding allegations made by former team-mate Frankie Andreu, who admitted in 2006 to taking EPO before the 1999 Tour - Armstrong's first victory - and his wife Betsy,
The duo testified in 2006 that they heard Armstrong tell a cancer doctor that he had doped with EPO in 1996. Armstrong swore, under oath, that it did not happen.
He told Winfrey that he had a 40-minute telephone conversation with the Andreus but he was not prepared to reveal what was said.