The United States Anti-Doping Agency (USADA) sent a letter Tuesday announcing formal doping charges against Lance Armstrong, according to sources at USADA.The decision to charge Armstrong came just as the statute of limitations was about to run out on Armstrong's final Tour de France win in 2005. The charges could put all seven of Armstrong's Tour de France titles at risk. He will also be banned from competition in triathlons, a sport he has been pursuing since retiring from cycling in 2011.The new action by USADA comes on the heels of a controversial February decision by the United States Attorney for Los Angeles, Andre Birotte Jr., to drop a criminal conspiracy and fraud investigation involving doping against Lance Armstrong and his former partners in the US Postal Service cycling team.60 Minutes reported on that investigation in its May 2011 story about Armstrong, which featured former Armstrong teammate Tyler Hamilton detailing how he personally witnessed doping by Armstrong. Hamilton confessed to using doping products throughout his career and while on the US Postal team as one of Armstrong's top lieutenants.The 60 Minutes story also reported for the first time that long-time Armstrong lieutenant George Hincapie told U.S. government investigators that he and Armstrong had "supplied each other with the blood booster EPO and discussed having used testosterone, another banned substance, during their preparation for races."In reaction to the new USADA charges, Armstrong issued a statement saying, "I have been notified that USADA ... intends to again dredge up discredited allegations dating back more than 16 years to prevent me from competing as a triathlete and try and strip me of the seven Tour de France victories I earned. These are the very same charges and the same witnesses that the Justice Department chose not to pursue after a two-year investigation. These charges are baseless, motivated by spite and advanced through testimony bought and paid for by promises of anonymity and immunity."60 Minutes reporting in May 2011 revealed that no fewer than three Armstrong teammates had told government investigators that they had personally witnessed Armstrong doping. Sources with knowledge of the allegations say that the USADA case will also rely on suspicious Armstrong test results from races in 2009 and 2010.