Seven-time Tour de France winner Lance Armstrong has described charges against him by the U.S. Anti-Doping Agency as "baseless [and] motivated by spite", according to BBC News.
The allegations against him include previously unpublicized claims of doping in 2009 and 2010, reports say.
The 40-year-old has been immediately banned from competing in triathlons, a sport he took up after his retirement from cycling in 2011.
"I have never doped," Armstrong said in a statement on his website. "These charges are baseless [and] motivated by spite."
In its 15-page letter, USADA said its investigation included evidence dating back to 1996 and accused Armstrong of a "pervasive pattern of doping" over many years.
It says it collected blood samples from him in 2009 and 2010 that were "fully consistent with blood ma¬nipu¬la¬tion including EPO use and/or blood transfusions".
More than 10 cyclists as well as cycling team employees witnessed Armstrong using performance-enhancing drugs and techniques, the letter says.
He could face a lifetime ban and be stripped of his awards if he is found to have used performance-enhancing drugs.
