US federal agents are investigating disgraced former Tour de France champion Lance Armstrong for crimes including obstruction, witness tampering and intimidation, ABC News reported Wednesday.

Citing an anonymous source, ABC News said the current probe is focused on different charges from those previously investigated in a federal probe that was dropped last year.

US Attorney Andre Birotte, who led the prior investigation, said he had no plans to press charges despite Armstrong's recent doping admissions, but he did not definitively rule out such action.

Birotte's investigation was centered on doping, fraud, conspiracy and Armstrong's denials of such crimes when he was the lead rider in the extremely successful government-funded US Postal Service Team.

"Obviously we've been well aware of the statements that have been made by Mr Armstrong and other media reports," Birotte said, referring to Armstrong's bombshell doping confession to chat show legend Oprah Winfrey last month.

"That has not changed my view at this time. Obviously we'll consider -- we'll continue to look at the situation," Birotte told reporters in Washington.

The ABC News source, quoted on condition of anonymity, said: "Birotte does not speak for the federal government as a whole. Agents are actively investigating Armstrong for obstruction, witness tampering and intimidation."

It's not, however, being done by FDA agents, who were prime among those who gathered evidence in the prior case against Armstrong.

US Food and Drug Administration (FDA) spokeswoman Sarah Clark-Lynn told AFP on Wednesday: "The FDA is not currently investigating on Lance Armstrong."

For years Armstrong denied doping, but he was banned last year after the US Anti-Doping Agency (USADA) gathered compelling testimony that he had been the ring-leader of a large-scale and highly-organized doping conspiracy.

Former teammate Tyler Hamilton opened the door to possible witness tampering charges against Armstrong in an interview with CBS News broadcast last month as part of a "60 Minutes" story with USADA chief Travis T. Tygart.

Hamilton told CBS that he was confronted by Armstrong in 2011 only three weeks after a prior interview with "60 Minutes" aired, in which Hamilton made revelations about Armstrong.

Hamilton told CBS he was in a crowded bar in Aspen, Colorado when Armstrong approached him.

"Turned to my right and it was Lance Armstrong," Hamilton said. "Stops me cold. First he asked how much '60 Minutes' had paid me to do that interview. Obviously, nothing.

"The biggest thing he said is: 'You know, we're going to make your life a living, f-ing hell, both in the courtroom and out.'"

Hamilton said he felt intimidated by Armstrong and, at that moment, Hamilton was a witness against Armstrong in what was an active federal investigation.

Armstrong was given a Wednesday deadline to come clean under oath about his doping activities -- and others who were involved in the cheating conspiracy -- in order to have any hope of USADA reducing his lifetime ban from competition.

Armstrong attorney Tim Herman told USA Today that Armstrong would not meet that deadline, saying his client wants to testify to the International Cycling Union (UCI).

USADA's evidence showed UCI officials might have turned a blind eye to enable Armstrong's doping scheme.

Armstrong faces other legal battles after being stripped last year of his record seven Tour de France titles.

Dallas insurance company SCA Promotions is set to sue Armstrong for $5 million, while Herman said Armstrong doesn't plan to repay the money.

SCA withheld a $5 million bonus due after Armstrong's sixth Tour de France win in 2004 because of doping allegations circulating in Europe, and Armstrong took them to court.

He won the case because SCA's original contract had no stipulations about doping.

SCA attorney Jeff Dorough told AFP that the firm expected to file a lawsuit against the 41-year-old on Thursday morning.