The Washington Post reported that USADA has written to Armstrong outlining charges that relate to allegations of doping that began in 1998 and continued until 2011.
According to the report, the charges include previously unpublicised allegations of doping in 2009 and 2010, after Armstrong came out of retirement.
The USADA was not immediately available for comment on the report.
In a statement on Wednesday night, Armstrong said: "I have been notified that USADA, an organisation largely funded by taxpayer dollars but governed only by self-written rules, 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.
"Although USADA alleges a wide-ranging conspiracy extended over more than 16 years, I am the only athlete it has chosen to charge. USADA's malice, its methods, its star-chamber practices, and its decision to punish first and adjudicate later all are at odds with our ideals of fairness and fair play.
"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.
"That USADA ignores this fundamental distinction and charges me instead of the admitted dopers says far more about USADA, its lack of fairness and this vendetta than it does about my guilt or innocence."
The charges brought by the USADA would immediately prevent Armstrong from competing as a triathlete, the sport he took up following his retirement from cycling in 2011.
Armstrong survived testicular cancer early in his career and went on to win seven consecutive Tour de France titles from 1999 to 2005 while competing for the US Postal Service team and the Discovery Channel team.
He retired after the 2005 Tour de France, but returned in 2009, riding for Astana Cycling and RadioShack before retiring for a second time in February 2011, taking up triathlon earlier this year.
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A statement on Wednesday night from the International Cycling Union, which did not name Armstrong, confirmed it had been notified of cases opened by USADA regarding several people.
"The UCI confirms that it has been informed by USADA of its decision to open anti-doping cases against a number of rider support personnel and a rider," the statement said.
"This is the first time USADA has communicated to UCI on this subject.
"The UCI is not aware of the information that is available to USADA on the persons concerned and has not been involved in the proceedings opened by USADA.
"The UCI will follow the case to the extent it will be informed and has noted that the persons concerned have been invited to send submittals on the allegations that are made against them.
"The UCI will not comment futher at this stage."