WASHINGTON — Seven-time Tour de France champion Lance Armstrong lashed out at the US Anti-Doping Agency on Wednesday, saying they want to brand him a drugs cheat based on "discredited" allegations.

"I have been notified that USADA, an organization 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," Armstrong said in a statement.

Armstrong said the witnesses cited by USADA were the same ones who spoke to federal investigators during a two-year probe which eventually ended without any criminal charges being brought.

"These charges are baseless, motivated by spite and advanced through testimony bought and paid for by promises of anonymity and immunity," Armstrong said.

"Although USADA alleges a wide-ranging conspiracy extended over more than 16 years, I am the only athlete it has chosen to charge," added Armstrong, who spoke of the agency's "malice" and "star-chamber practices".

The Washington Post reported Wednesday that USADA had written to Armstrong and seven others alleging the agency had collected blood samples from Armstrong in 2009 and 2010 that were "fully consistent with blood manipulation including EPO use and/or blood transfusions."

According to the Post, which obtained a copy of the letter, USADA claims it has witnesses to the fact that Armstrong and five former cycling team associates -- including Italian doctor Michele Ferrari and cycling team manager Johan Bruyneel -- engaged in a doping conspiracy from 1998-2011.

USADA officials could not immediately be reached for comment on Wednesday.

Armstrong, who won the Tour de France from 1999-2005 and used his fame to fuel his charitable work for cancer awareness, has vehemently denied using performance-enhancing drugs during his cycling career.

He has never tested positive, but has been publicly accused by former teammates Floyd Landis and Tyler Hamilton -- both admitted drugs cheats -- of doping.

When US prosecutors dropped their probe of Armstrong and other cyclists without bringing charges in February, USADA said it would continue to probe allegations of doping in cycling and hoped to have access to the information gathered in the criminal probe.

"Unlike the US Attorney, USADA's job is to protect clean sport rather than enforce specific criminal laws," USADA chief executive Travis Tygart said in February.

Armstrong, however, accused the agency of a "vendetta".

"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," he said.

"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."