Armstrong could provide information that might get his ban reduced to eight years. By then, he would be 49. He returned to triathlons, where he began his professional career as a teenager, after retiring from cycling in 2011, and has told people he's desperate to get back.
Initial reaction from anti-doping officials ranged from hostile to cool.
WADA president John Fahey derided Armstrong's defense that he doped to create "a level playing field" as "a convenient way of justifying what he did — a fraud."
"He was wrong, he cheated and there was no excuse for what he did," Fahey said by telephone in Australia.
If Armstrong "was looking for redemption," Fahey added, "he didn't succeed in getting that."
USADA chief Travis Tygart, who pursued the case against Armstrong when others had stopped, said the cyclist's confession was just a start.
"Tonight, Lance Armstrong finally acknowledged that his cycling career was built on a powerful combination of doping and deceit," Tygart said. "His admission that he doped throughout his career is a small step in the right direction. But if he is sincere in his desire to correct his past mistakes, he will testify under oath about the full extent of his doping activities."