Armstrong, who retired from cycling last year, could face a lifetime ban from the sport if he is found to have used performance-enhancing drugs.
The story was first reported Wednesday by the Washington Post.
The charges from USADA come just months after federal prosecutors closed a two-year criminal investigation of Armstrong without indicting him.
Armstrong maintained his innocence, saying: "I have never doped, and, unlike many of my accusers, I have competed as an endurance athlete for 25 years with no spike in performance, passed more than 500 drug tests and never failed one."
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