Shamed cyclist Lance Armstrong has admitted that he used performance-enhancing drugs, US media reported on Tuesday, as the sport braced for revelations in his first interview since being banned for life for doping.

Armstrong, who has consistently denied drug-taking, on Monday recorded a two-and-a-half hour interview with chat show host Oprah Winfrey at his home in Austin, Texas, where a media scrum gathered hoping for a glimpse of the fallen icon.

His representatives refused to reveal what was discussed but the New York Times and USA Today newspapers both cited sources with knowledge of the taping that the seven-time Tour de France winner would admit using banned substances in his career.

The Times added that he would also testify against high-ranking cycling officials who knew he was doping and may have helped him do it.

Armstrong, the most high-profile cyclist of recent years, was stripped of his career wins and banned for life last year after the US Anti-Doping Agency (USADA) said he was at the centre of the biggest doping programme ever seen in sport.

The revelations against the Texan and reams of damning eye-witness testimony from former teammates plunged cycling into crisis, amid claims of complicity and cover-up, while big-name corporate sponsors dropped the rider after years of support.

Winfrey, who was set to promote the edited, 90-minute version of the interview on CBS television's "This Morning" program on Tuesday, said only on Twitter: "He came READY!"

Before taping, 41-year-old Armstrong personally apologized to staff members at Livestrong, the charity he founded in 1997 to support cancer survivors.

"Lance came to the Livestrong Foundation's headquarters today for a private conversation with our staff and offered a sincere and heartfelt apology for the stress they've endured because of him," Livestrong spokeswoman Rae Bazzarre told AFP.

The announcement that Armstrong had agreed to an interview sparked widespread speculation that he might finally confess to being a drug cheat after years of adamant denials and in the face of mounting evidence.

The New York Times, citing unnamed sources familiar with Armstrong's situation, said he was planning to testify against officials from the International Cycling Union (UCI) governing body about their involvement with doping.

But he would not testify against fellow riders, the report said.

Armstrong was also in talks with the US Department of Justice regarding his possible testimony in a federal whistle-blower suit involving his former team, which was sponsored by the US Postal Service, the daily added.

A former teammate who was stripped of his 2006 Tour de France win, Floyd Landis, filed that suit against Armstrong and other team principals, alleging they defrauded the government because the riders were doping in violation of their contracts.

Armstrong is believed to be willing to admit to doping and cooperate in other pending legal proceedings in order to pave the way for USADA to lift his lifetime ban so that he can return to competing in marathons and triathlons.

His years of dominance on the Tour de France, the sport's greatest race, raised cycling's profile in the United States to new heights.

It also gave the Texan -- diagnosed in 1996 with late-stage testicular cancer that had spread to his brain and lungs -- a unique platform to promote cancer awareness and research.

The Lance Armstrong Foundation has raised almost $500 million since its creation 16 years ago.

In the wake of the allegations, several top sponsors such as sportswear giant Nike dumped Armstrong, and on November 14, Livestrong dropped his name from the foundation.

On the legal front, since the UCI effectively erased Armstrong from the record books, The Sunday Times of Britain has sued him for more than £1 million ($1.6 million) over a 2006 libel payment.

It had paid Armstrong £300,000 to settle a libel case after publishing a story suggesting he may have cheated, and now wants that money, plus interest and legal costs, repaid.

A Texas insurance company has also threatened legal action to recoup millions of dollars in bonuses it paid him for multiple Tour victories.