Chambery - Lance Armstrong said on Wednesday he will cooperate with a "fair investigation" but not a "witch hunt" into allegations that he and his former cycling team were involved in doping.
Armstrong was responding to reports of a US federal investigation of possible fraud and doping charges against him and former associates.
He spoke before the 10th stage of the Tour de France, where he is 31st overall.
The New York Times reported that US authorities have issued grand jury subpoenas to witnesses as part of the probe into allegations made by American cyclist Floyd Landis.
Landis, who was stripped of his 2006 Tour title for doping, said the use of banned substances was common on the US Postal team when he rode with Armstrong.
"Like I said, as long as we have a legitimate and credible and fair investigation, we'll be happy to cooperate, but I'm not going to participate in any kind of witch hunt," the seven-time Tour de France winner and cancer survivor said. "I've done too many good things for too many people."
Armstrong said he had not been subpoenaed or contacted by lead investigator Jeff Novitzky. He said he wasn't aware of any riders who have been subpoenaed.
Armstrong claimed stories are being leaked to the media as part of an "agenda" against him and questioned the need for a federal probe.
"Would the American people feel like this is a good use of their tax dollars?" he said. "That's for them to decide."
Armstrong has said that Landis, who recently admitted to doping after years of denials, cannot be believed. He also said he didn't believe that other riders had come forward with similar allegations.
"I don't think the government will build a case on Floyd Landis," said Armstrong, who has never tested positive for use of banned substances. "His credibility left a long time ago."
Armstrong said the allegations should be investigated by the international cycling body, UCI, or the World Anti-Doping Agency.
"If you think that you have an athlete that's broken the rules - this is not baseball, this is not football ... we have a governing body to deal with that," he said. "I have had 500 (doping) controls in my day. USADA deals with that, the UCI deals with that. WADA deals with that. We have an agency to deal with that. I have no problem playing by those rules."
Armstrong has repeatedly denied any involvement in doping and reiterated that position again on Wednesday.
"As long as I live I will deny that," he said. "There is absolutely no way I forced people, encouraged people, told people, helped people, facilitated ... Absolutely not. 100%."
Armstrong also denied that he was ever a part owner of the Postal Service team, which was owned by Tailwind Sports.
"I was a rider on the team, I was contracted with Tailwind Sports, I never had any dealings - ANY - with the Postal Service - zero," he said.
"I didn't own the company. I didn't have an equity stake. I didn't have a profit stake, I didn't have a seat on the board. I can't be any clearer than that."