OSLO (Reuters) - Norwegian cyclist Steffen Kjaergaard, who competed with the disgraced Lance Armstrong on the U.S. Postal Service team in the Tour de France in 2000 and 2001, admitted to doping on Tuesday.

"When I was a part of the U.S. Postal Service team, everything was organized by the team. I did not need to arrange for a doctor or do anything by myself," retired Kjaergaard told a news conference.

"The reason that I am coming forth now is that I have had a big problem with my own conscience."

Armstrong was stripped of his seven Tour de France titles and banned for life on Monday after the International Cycling Union (UCI) ratified the United States Anti-Doping Agency's (USADA) sanctions against the American for taking drugs.

Kjaergaard said he began using banned substances - primarily erythropoietin (EPO) and cortisone - in 1998, before joining the U.S. Postal Service team. He denied being aware of team-wide doping.

"I cannot say if any of my team mates were using illegal substances," Kjaergaard said. "I can assume that others at U.S. Postal were using something that the witness reports said. I have no direct knowledge though."

Armstrong, who denies wrongdoing, lost his 1999-2005 titles after former team mates testified against him and themselves, describing what USADA called the "most sophisticated, professionalized and successful doping program that sport has ever seen".

(Reporting by Vegard Botterli; writing by Balazs Koranyi, editing by Mark Meadows)