The U.S. Anti-Doping Agency is set to bring doping charges against Lance Armstrong that could lead to his being stripped of his seven Tour de France titles.

Armstrong, 40, has fought off doping accusations for more than a decade, including coming out on top when a two-year federal investigation into his alleged doping-related crimes was dropped four months ago.

This time, though, the accuser is the anti-doping agency, which does not have the power to bring criminal charges but does have the power to strip him of the accolades that helped make him the most famous cyclist in history.

If its charges are upheld, the agency — a quasi-governmental organization that oversees anti-doping mostly in Olympic sports — could also levy a lifetime ban on him from competing in elite events.

The case already has led to his being barred from competing in triathlons, a sport he has focused on since retiring from cycling last year.

This time, unlike in the government’s investigation of him, the anti-doping agency’s bar to charge and eventually punish him is not as high.

“It’s serious in the sense that they’ve got the ability to take away his title and ban him from future events,” said Robert D. Luskin, one of Armstrong’s lawyers. “Is it a process that is likely to lead to something that gives us some confidence that the allegations are true? Not for a second.”

Luskin said Armstrong was notified of the charges last week and was given a week to meet with the anti-doping agency officials and confess. He declined because the agency offered little information about the case.

Armstrong, who had hoped to qualify for the Ironman World Championship in the fall, said that he had never doped and that the anti-doping agency had a vendetta against him, fueled by what he called malice.

“These charges are baseless, motivated by spite and paid for by promises of anonymity and immunity,” he said in a statement. On Twitter, he called the agency’s inquiry “a witch hunt,” and tagged his post with “#unconstitutional.”

The anti-doping agency, in a letter sent to Armstrong and five of his cycling colleagues Tuesday, said that Armstrong and his associates were at the heart of several teams’ systematic doping programs from 1996 through 2010.

The letter, first reported by The Washington Post on Wednesday, describes some of the evidence against Armstrong. The accusations include that he was part of teamwide doping schemes from 1996 through 2010, when he was with four squads: the U.S. Postal Service team, the Discovery Channel team, the Astana team and the RadioShack team.

“The witnesses to the conduct described in this letter include more than 10 cyclists as well as cycling team employees,” the letter said.

Armstrong is specifically accused of using the blood-booster EPO, blood transfusions, testosterone, human growth hormone corticosteroids and saline and plasma infusions to boost performance or mask use of banned substances. He also is charged with distributing and administering some of those doping agents and methods, a violation of the World Anti-Doping Agency’s code that could result in a four-year to a lifetime ban.

Multiple riders will testify that Armstrong gave them, encouraged them or assisted them in using banned substances, the letter said.

The U.S. agency also said results from blood tests done on Armstrong in 2009 and 2010 by the International Cycling Union are “fully consistent with blood manipulation including EPO use and/or blood transfusions.”

The letter also said that other people are facing charges of systematic doping on Armstrong’s teams: Johan Bruyneel, who is Armstrong’s longtime team manager; Pedro Celaya and Luis Garcia del Moral, two team doctors; Michele Ferrari, a consulting doctor who helped train Armstrong; and Pepi Marti, a team trainer. They also face lifetime bans.

Considering that Armstrong has an army of high-powered lawyers, including those that worked with him during the federal inquiry, the antidoping agency has its work cut out for it. But Travis Tygart, chief executive of the agency, said it is ready.

“We do not choose whether or not we do our job based on outside pressures, intimidation or for any other reasons other than the evidence,” he said.

Armstrong still has not decided whether to fight the charges.

“Lance has never shrunk from a fair fight, and we haven’t decided whether or not this process affords him a fair opportunity to meet the charges head on,” Luskin said.