Lance Armstrong has admitted using performance enhancing drugs in an interview with Opray Winfrey due to be aired later this week.
The American was stripped of his seven-time Tour de France titles after the US Anti-Doping Agency (Usada) accused him of being at the centre of "the most sophisticated, professionalised and successful doping programme" the sport has ever seen.
Armstrong has stayed publicly silent on the accusations since their findings were revealed last year.
However, the announcement that he was to conduct an interview with Winfrey, which was filmed last night and will be aired at 2am GMT this Friday, led to speculation he would finally come clean.
An unnamed source in America close to the interview has told the New York Times, USA Today and the Associated Press news agency that he admitted to doping during the interview.
Before taping the interview, which was conducted at his home in Texas, Armstrong apologised to around 100 staff at his Livestrong cancer foundation. The cyclist was said to have choked up as he spoke to members of the charity, during which he said: "I'm sorry".
It is understood he did not make a direct confession about drugs to the Livestrong team. Instead, he is said to have apologised for letting them down, and for putting the foundation, which he chaired until last year, at risk.
A confession from Armstrong would mark a major reversal, who in the past has repeatedly denied the allegations.
It remains unclear how far Armstrong will go in his confession, although the cyclist sent a text message to the AP stating: "I told her [Winfrey] to go wherever she wants and I'll answer the questions directly, honestly and candidly. That's all I can say."
Armstrong will be aware that revealing details of his doping could have consequences. For more than a decade, Armstrong dared anybody who challenged his version of events to prove it, including in court. He scolded some in public and didn't hesitate to punish outspoken riders during the race itself. He waged legal battles against others in court.
At least one of his opponents, the London-based Sunday Times, has already filed a lawsuit to recover about $500,000 it paid him to settle a libel case, and Dallas-based SCA Promotions, which tried to deny Armstrong a promised bonus for a Tour de France win, has threatened to bring another lawsuit seeking to recover more than $7.5million awarded by an arbitration panel.
Reports have suggested Armstrong's decision to finally come clean is to pave the way to compete in triathlons, which his current ban excludes him from doing.