WASHINGTON (AFP) - Fallen cycling legend Lance Armstrong took a major legal risk in confessing to drug use in a television interview and has exposed himself to significant litigation, lawyers warned on Friday.

The seven-time Tour de France champion already faced several potential lawsuits from former teammates and sponsors who claim they were hurt by his doping and by his ferocious but ultimately unsuccessful attempt to cover it up.

Yet by appearing with talk show queen Oprah Winfrey and bluntly admitting to taking a cocktail of banned substances over a decade and a half while bullying those around him, he may have put more than his reputation at risk.

"I think it's going to be a big judgment against him. I think he's going to have a gigantic money judgment," said Mr Peter Keane, a law professor at Golden Gate University in San Francisco.

Armstrong's admission of guilt could force him to pay substantial out of court settlements to many of his detractors, and may encourage United States (US) authorities to add their weight to one of the most serious cases against him.

Meanwhile, his aggressive demeanour and perceived lack of contrition in the interview could turn judges and jurors against him if cases come to court, and will increase the determination of those seeking to sue him.

"He did a terrible job," said Mr Jordan Kobritz, a former lawyer and head of sports at SUNY Cortland university, reflecting the view of many sports fans and professionals reacting on social networks and in television studios.

"I didn't think he was sincere, contrite, forthright or remorseful," he told Agence France-Presse (AFP) after the first part of the interview was broadcast late on Thursday. "As a former attorney, I think his attorneys probably weren't in favour of what he did, because of the many potential legal consequences. I think they were right."

Mr Kobritz said Armstrong missed an opportunity to make a genuine apology to two women, former team masseuse Emma O'Reilly and a teammate's wife Betsy Andreu, whom he had insulted when they attempted to reveal his doping.

"He ruined their life, he called them some violent names," said Mr Kobritz, predicting the women would launch defamation suits. "He basically blew that opportunity. He basically incited them to come after him.

"The most logical result would be a settlement. He will be buying them off."

But that might not even be Armstrong's biggest legal challenge.

The US Department of Justice is close to making a decision on whether to add the government's name to a complaint lodged in 2010 against Armstrong by former fellow US Postal Service teammate Floyd Landis.

The Postal Service, a federal agency, paid US$30 million (S$37 million) in public money to sponsor Armstrong's team - and may now seek to get it back.

Mr Keane said that a decision to drop a previous Department of Justice probe into Armstrong had been unpopular within the agency, and that many officials would be keen to reopen the inquiry following his admission.

"Now with him coming out, sort of daring the government to do anything, there will be tremendous pressure within the government and the Department of Justice to reopen and go forward," he told AFP.

"Otherwise, it looks like this guy is totally above the law."

Mr Keane said that in addition to civil litigation, Armstrong could find himself prosecuted for lying to federal investigators during previous investigations or to obtaining sponsorship through criminal fraud.

And the tone of the interview with Winfrey has not helped his case.

"He's a totally narcissistic, driven person who'd destroy other people to achieve his ends," Mr Keane said.

"It's just so clearly self-serving that he wants to come back into competition and celebrity and to achieve the power that he had. No one is going to believe that."