The U.S. Anti-Doping Agency had told Armstrong he would have to reveal all knows about doping in cycling — a process officials expected would take several days — if he wanted to reduce his lifetime ban from sports.
Wednesday was the latest deadline for Armstrong to decide on USADA's offer. After negotiating with the agency for two months, he refused.
Armstrong attorney Tim Herman said the cyclist "will not participate in USADA's efforts to selectively conduct American prosecutions that only demonize selected individuals while failing to address the 95 percent of the sport over which USADA has no jurisdiction."
USADA chief executive Travis Tygart said the agency had expected Armstrong would agree to talk and would be "moving on" without him.
"Over the last few weeks he has led us to believe that he wanted to come in and assist USADA, but was worried of potential criminal and civil liability if he did so," Tygart said. "Today we learned from the media that Mr. Armstrong is choosing not to come in and be truthful and that he will not take the opportunity to work toward righting his wrongs in sport."
Herman has said Armstrong is willing to participate in an international effort to clean up cycling, an effort that has broken down in spats between the International Cycling Union, the sport's governing body, and the World Anti-Doping Agency.
"He will be the first man through the door, and once inside will answer every question, at an international tribunal formed to comprehensively address pro cycling, an almost exclusively European sport," Herman said.
For more than a decade, Armstrong denied using performance-enhancing drugs. But last year, USADA released a report that detailed extensive doping on his Tour de France-winning teams and stripped him of those victories. Armstrong then admitted last month in an interview with Oprah Winfrey that he doped to win those races.
Tygart has accused Armstrong of lying in portions of that interview, most notably Armstrong's claim that he raced clean when he came out of retirement in 2009-2010. USADA's report says blood evidence shows Armstrong cheated during his comeback.
USADA also wants to question Armstrong under oath about whether cycling officials helped him cover up positive drug tests during his career, charges he continues to deny.
Beyond his problems with USADA, Armstrong still faces several legal challenges.
Armstrong was the subject of a two-year federal grand jury investigation that was dropped a year ago without an indictment, but the Department of Justice is still considering whether to join a federal whistle-blower lawsuit filed by former Armstrong teammate Floyd Landis.
Armstrong also has been sued by a Dallas-based SCA Promotions to recover more than $12 million in bonuses. And he has been sued by The Sunday Times in London to recover a libel judgment that the cyclist won against the paper.
Armstrong's latest decision means he won't risk the legal exposure a sworn interview with USADA might create for those cases or new ones yet to come. The possibility of reducing his ban likely carried little incentive for the 41-year-old Armstrong, who had moved his athletic career into running and competing in triathlons.
Under international anti-doping rules, Armstrong's lifetime ban could only be reduced to eight years, by which time Armstrong will be nearly 50 years old.