Armstrong himself confirmed on Wednesday that he was facing fresh doping allegations from the US Anti-Doping Agency (USADA).

The 40-year-old, who has been dogged by drug allegations throughout his career, condemned the charges as "baseless, motivated by spite."

Armstrong, training for a triathlon in France, said the agency intended “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."

A 15-page letter obtained by media organizations is reported to contain allegations that Armstrong had used drugs such as the red-blood-cell-boosting EPO, as well as testosterone, cortisone, masking agents and human growth hormone.

While Armstrong has never tested positive in the past, the letter said blood samples taken in 2009 and 2010 were "fully consistent with blood manipulation including EPO use and/or blood transfusions."

Allegations against team members

Specific examples are not cited and the charges are apparently based on evidence gathered in an investigation of Armstrong's teams.

The USADA said in a statement that three doctors and two officials associated with the United States Postal Service Team - Armstrong's team at the peak of his career - had also been given "written notice of allegations of anti-doping rule violations."

A "massive doping conspiracy," from 1998 to 2011 is alleged in the letter.

The USADA's allegations mean that Armstrong is immediately banned from triathlon competition, which he took up after retiring from competition cycling last year. Armstrong's Tour de France wins came between 1999 and 2005.

US federal prosecutors closed a two-year criminal investigation into the matter in February, without bringing charges.

rc/jm (AFP, AP, dpa, Reuters)