US Attorney Andre Birotte, who led a federal investigation into the disgraced rider, did not definitively rule out action, but said Armstrong's public admission had not yet changed the decision not to prosecute.
"We made a decision on that case, I believe, a little over a year ago," he said, when asked about the status of the federal inquiry into long-standing claims that Armstrong had run a doping program and had lied to federal agents.
"Obviously we've been well aware of the statements that have been made by Mr Armstrong and other media reports," he said, referring to Armstrong's bombshell 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, but that hasn't changed our view as I stand here today," Birotte told a news conference in Washington.
The 41-year-old Texan was stripped of his record seven Tour de France titles last year after the US Anti-Doping Agency gathered compelling testimony that he had been the ring-leader of a large-scale doping conspiracy.
He had long angrily professed his innocence, including in questioning by US federal agents investigating the same allegations, but the mask fell away last month when he confessed his guilt to Winfrey in detail.
The admission threw up a number of legal questions, including whether the federal probe might be re-opened, whether he might be prosecuted for perjury and whether he might be sued to recover former payments and prize money.
Dallas insurance company SCA Promotions has already demanded the return of $12 million in bonuses it paid to Armstrong for multiple Tour titles.
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, and Armstrong attorney Tim Herman told USA Today that the shamed cyclist doesn't intend to pay back any of the money.
"My only point is no athlete ever, to my understanding, has gone back and paid back his compensation," Herman told the newspaper in an article published Tuesday.
Herman cited New Orleans Saints coach Sean Payton, who was suspended for a season by the NFL for the team's alleged pay-for-hits "bounty" scheme.
"They were suspended, but nobody said you've got to give your paycheck back," Herman said.
While Armstrong told Winfrey he would like to get his lifetime ban reduced, so that he could eventually compete in marathons, for example, by the time he's 50, Herman said the shamed cyclist was now prepared to cooperate with anti-doping authorities in a bid to clean up cycling even if is eligibility isn't restored.
"Whether it's a Truth and Reconciliation Commission or some comprehensive attempt to clean things up, it doesn't make any difference as long as something like that is convened," Herman said. "Lance will definitely cooperate."
Herman told the newspaper that Armstrong doesn't believe that USADA is best-placed to lead the battle against doping in cycling, since the sport is largely based in Europe.
Nor has USADA chief Travis Tygart's claim that Armstrong lied in some of his comments to Winfrey eased relations between the two parties.
"To hear Tygart tell it, Lance Armstrong is responsible for the culture he was dropped into on a team (that) was engaged in misconduct long before he got to the team," Herman said.
"He was a 19-year-old kid dropped in this culture, just like everybody else. He didn't create it."
