LOS ANGELES — The United States Anti-Doping Agency (USADA) has set disgraced cyclist Lance Armstrong a Feb. 6 deadline to fully cooperate in the investigation into cycling's darkest episode in return for a possible reduction of his life ban. In excerpts of his interview with the CBS network scheduled for Sunday broadcast, USADA CEO Travis Tygart said he had written a letter to Armstrong with the offer. Armstrong, 41, admitted in an interview with Oprah Winfrey last week that he had cheated his way to a record seven Tour de France titles with systematic use of banned, performance-enhancing drugs. Last year he was stripped of his titles after being labeled a "serial cheat" by the USADA. Tygart said if Armstrong wants to lessen his lifetime sporting ban he must "cooperate fully and truthfully" about drug-taking in the sport. It is not clear if cooperation from Armstrong could take the form of testimony before a truth and reconciliation commission. The International Cycling Union (UCI), which is under pressure from the World Anti-Doping Agency and USADA, Friday agreed that such a platform would benefit the drug-damaged sport after a series of devastating doping cases. Armstrong, a cancer survivor who during the Oprah interview admitted doping for the first time after years of vehement denials, said he would be willing to testify before such a commission if he were invited. He also said that his record seven wins in the tour — between 1999-2005— were fueled by performance enhancing drugs but insisted he was clean when he came out of retirement and raced in the Tour de France in 2009 and 2010. Tygart disputed Armstrong's claims of a clean comeback in 2009. "His blood tests in 2009, 2010 ... one to a million chance that it was due to something other than doping," Tygart said. The USADA chief reiterated the assertions in the report issued last year by the agency on which it based its lifetime ban of Armstrong and the forfeiture of all his cycling results from August 1998. The report led to Armstrong's demise after more than a decade of denials that he was a drug cheat during which he pursued a series of vitriolic attacks against several individuals who had accused him of doping. Tygart told CBS that Armstrong may have lied about doping after his comeback because under the statute of limitations for criminal fraud, he would still be open to prosecution. He also took issue with Armstrong's claim that the disgraced Texan's favored drug cocktail of blood-boosting EPO, blood transfusions and testosterone included just a small amount of EPO. "He used a lot of EPO," Tygart told "60 Minutes", alleging that Armstrong was less than truthful when he told Winfrey that he had not pushed his teammates toward cheating. "He was the boss," Tygart said in the excerpt. "The evidence is clear he was one of the ringleaders of this conspiracy that pulled off this grand heist that ... using tens of millions of taxpayer dollars defrauded millions of sports fans and his fellow competitors." — Agencies