Washington - Seven-time Tour de France champion Lance Armstrong confirmed on Wednesday he is facing new doping allegations brought by the US Anti-Doping Agency that could result in the stripping of his titles.
Armstrong - who has vehemently denied using performance-enhancing drugs during his career - angrily said the new "baseless" charges stem from "discredited" allegations from the past.
"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," Armstrong said in a statement.
He slammed the agency as "an organisation largely funded by taxpayer dollars but governed only by self-written rules."
The Washington Post was among the media outlets reporting Wednesday that USADA had written to Armstrong saying blood samples taken from him in 2009 and 2010 - when he came out of retirement - were "fully consistent with blood manipulation including EPO use and/or blood transfusions."
Armstrong finished third in the Tour de France in June of 2009 and 23rd in the event in 2010.
Since retiring again from cycling last year, Armstrong has taken up triathlon competition, but USADA's action immediately bans him from competing.
USADA chief executive Travis Tygart issued a statement confirming "that written notice of allegations of anti-doping rule violations was sent yesterday to him (Armstrong) and to five additional individuals all formerly associated with the United States Postal Service professional cycling team.
"These individuals include three team doctors and two team officials.
"This formal notice letter is the first step in the multi-step legal process for alleged sport anti-doping rule violations," Tygart said.
The next step is for Armstrong to answer the charges, in writing, by June 22.
According to the Post, which obtained a copy of the letter to Armstrong, 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.
Armstrong, however, said the witnesses cited by USADA were the same ones who spoke to federal investigators during a two-year probe that ended in February without any criminal charges being brought.
He called the charges "baseless" and "motivated by spite," adding that the fact that other cyclists weren't charged demonstrates USADA's "vendetta" against him.
Tygart said USADA's case was supported by evidence, but that until the process was complete, those involved were presumed innocent.
"We do not choose whether or not we do our job based on outside pressures, intimidation or for any reason other than the evidence," Tygart said.
"Our duty on behalf of clean athletes and those that value the integrity of sport is to fairly and thoroughly evaluate all the evidence available and when there is credible evidence of doping, take action under the established rules.
"As in every USADA case, all named individuals are presumed innocent of the allegations unless and until proven otherwise through the established legal process."
Tygart said that if the case continues, it will not, in fact, be USADA that determines whether Armstrong is guilty of doping.
"If a hearing is ultimately held then it is an independent panel of arbitrators, not USADA that determines whether or not these individuals have committed anti-doping rule violations as alleged," Tygart said, adding that USADA would not comment further on the evidence or the issue "unless or until it is appropriate".
Armstrong, who won the Tour de France from 1999-2005 and used his fame to fuel his charitable work for cancer awareness, has never tested positive.
But he has been publicly accused by former teammates Floyd Landis and Tyler Hamilton - both admitted drugs cheats - of doping.
"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," Armstrong 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."