Sinkewitz admitted to "incorrect conduct" just hours after being dismissed by his team for refusing to have his backup sample tested.

T-Mobile had initially suspended Sinkewitz after he tested positive for elevated testosterone levels during training on June 8 — a month before the start of the Tour de France. He competed in the race until he crashed into a spectator during the eighth stage on July 15.

Today, Sinkewitz said he had obtained Testogel, a substance he said is used on the skin to balance out a testosterone deficit.

The substance "is supposed to aid better recuperation during hard training exercises," he said in a statement on his Web site.

"Without thinking, or simply in great stupidity, I had applied Testogel secretly to my upper arm at the training camp in France on the evening before the doping test," Sinkewitz said, without specifying whether he knew the substance was banned. "I did it instinctively and without thinking about the possible consequences."

T-Mobile fired Sinkewitz after the German Cycling Federation said the 26-year-old rider declined to have his B sample analyzed.

"For the team, this means that it is a positive doping case," T-Mobile spokesman Christian Frommert said. "That means he will be fired by the team."

T-Mobile said in a statement that its sporting director, Rolf Aldag, expects a "complete and comprehensive explanation" from Sinkewitz.

"Patrik needs to come clean on everything, so some light can be shed on this affair," he said.

Later today, German mineral water producer Foerstina said it was ending its sponsorship contract with Sinkewitz.

Sinkewitz had signed the International Cycling Union's new anti-doping charter that commits riders to promise that they are not involved in doping and agree to pay a year's salary on top of a two-year ban if caught doping.

"It was a big mistake and irresponsible toward the team, my colleagues, the sponsor and the whole of cycling to use Testogel," Sinkewitz said Tuesday. "I could have achieved my performance without it."

Sinkewitz said he wants to help bring about "a new cycling without doping" in future.

His case was the latest to shake German cycling in the past few months.

Several former riders for Telekom, now renamed T-Mobile, admitted using performance-enhancing drugs in the 1990s, including Bjarne Riis, a Dane who won the Tour de France in 1996.

Jan Ullrich, who won the 1997 Tour, has denied any wrongdoing but retired in February after being implicated in the Spanish blood-doping scandal known as Operation Puerto.

T-Mobile's current anti-doping program is considered among the most rigorous in cycling.