Armstrong has said those witnesses were given “sweetheart deals” and offers of lenient punishments regarding their own doping admissions to testify against him. Still, he pre-empted any potential embarrassment from that hearing by announcing Thursday that he would no longer contest the doping charges, a decision that was taken by antidoping officials as an admission of guilt.

The United States Anti-Doping Agency said Friday that it was sanctioning Armstrong for using the banned blood booster EPO, blood transfusions, testosterone, corticosteroids and masking agents; for trafficking EPO, testosterone and corticosteroids; and for administering those drugs to other riders. The agency also claimed he participated in a widespread cover-up of doping on his Tour-winning teams.

The agency then said it would move to expunge Armstrong’s most celebrated cycling achievements — his seven Tour de France titles — and bar him for life from participating in any sport that follows the World Anti-Doping Code.

In the next several weeks, the agency is obliged to send Armstrong, the International Cycling Union and the World Anti-Doping Agency a detailed explanation of why it sanctioned Armstrong. Each party can then appeal the ruling to the Court of Arbitration for Sport.

The antidoping agency has said its evidence includes blood profiles from 2009 and 2010 that were consistent with doping, which means they showed blood results that were outside his normal range.

“This is not an adverse finding, but this is certainly a sufficient equivalent to testing positive,” said Christiane Ayotte, the head of a World Anti-Doping Agency-accredited lab outside Montreal. “We’re at the point that if we’re not using these indirect markers, you can just forget about a case. For example, oral testosterone and microdoses of EPO will be detectable for only 12 hours. You just about have to be there when the athlete is doping to catch them.”