Telekom, the team's main sponsor, also is considering terminating its relationship with the team, which bears the name of its subsidiary. That could lead car company Audi and bike manufacturer Giant to follow suit.
"Obviously its a long story of doping and discussions with Telekom," Jim Runau, Adidas Group spokesman, told The Associated Press on Thursday. "We have told Telekom of our decision and we are in talks to get out of the contract early."
Runau said Adidas, whose contract runs through 2008, has been talking to Telekom about the doping problems since last year's scandal-ridden Tour de France. The companies have other intertwining sponsorships, including Bayern Munich and Germany's national team.
Adidas won't say what its deal with T-Mobile is worth.
Telekom is the team's biggest sponsor at a reported 10 million EUR(US$14.5 million) annually.
Adidas called former T-Mobile rider Lukas Sinkewitz's recent testimony to the German cycling federation a final straw.
Sinkewitz said doping continued at the team in 2006, later than previously known. He described going to the University of Freiburg clinic for illegal own-blood doping from two former T-Mobile doctors.
Sinkewitz was tested before this year's Tour de France, and the announcement of his positive test during the race landed like a bombshell in Germany. German television and sponsors thought the two main German teams had cleaned up their acts after years of doping scandals.
Television dropped coverage of the Tour and sponsors began to end contracts. Gerolsteiner will not continue to sponsor Germany's other ProTour team after 2008.
Telekom's board met on Tuesday to rethink a contract it extended in August to 2010. A decision to drop the sport would have repercussions in Germany.
"Cycling is permanently under examination at the moment. We will wait to see what happens at Telekom," Audi spokesperson Iris Altig said.
Telekom has asked for a copy of Sinkewitz's testimony.
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