The scandal surrounding T-Mobile rider Patrik Sinkewitz's failed drugs test, the decision by German rider Andreas Klöden’s team Astana to quit the Tour de France and the months of revelations and allegations over doping have plunged German cycling into an "existence-threatening crisis," the German Cycling Federation (BDR) said on Tuesday.

And things could get worse. With Sinkewitz set to find out if the B sample of his June 8 drug test matches the A sample that showed abnormal levels of testosterone, German cycling is bracing for another high-profile doping confession to add to the many others which have brought the sport into the spotlight for all the wrong reasons this year.

Sinkewitz's B sample is expected to be tested next Tuesday and the BDR was keen to talk to the cyclist. "Of course, we want to talk through the situation with Patrik," BDR president Rudolf Scharping -- Germany's former Minister of Defense -- told German sports news agency SID.

Germany's biggest team under threat

T-Mobile have suspended Sinkewitz pending the results of his second sample, and the team -- as well as the sport in general -- is reeling from a series of recent blows.

Earlier this year, seven former Telekom (T-Mobile's previous name) riders, including now disgraced 1996 Tour de France winner Bjarne Riis and sprinter Erik Zabel, confessed to using banned blood-booster erythropoietin (EPO). German cycling legend Jan Ullrich was also embroiled in a doping scandal, though no charges have been brought against him.

The future hangs in the balance for Germany’s biggest cycling team as the German mobile operators who sponsor the team are set to make an announcement after the current Tour ends on Sunday as to whether they will continue to fund T-Mobile.

If the sponsors choose to leave the sport it will be a devastating blow to cycling in Germany, which has watched as German television channels ARD and ZDF largely cancelled their coverage of this year's Tour after Sinkewitz's failed test.

German sportswear giant Adidas has said it is also considering pulling out of their partnership agreement with T-Mobile and the German cycling team in protest.

Klöden suffers as team pulls out

Doping, meanwhile, has ended the Tour for another German rider, albeit because of a teammate's usage. Andreas Klöden was fifth in the Tour’s overall standings when Alexandre Vinokourov of Kazakhstan tested positive in the A sample for a homologous blood transfusion. The results suggest Vinokourov underwent a blood transfusion shortly before the start of the stage.

"Alexandre Vinokourov was tested positive for a blood transfusion and the team is leaving the Tour," Astana spokeswoman Corinne Druey said on Tuesday.

Using this technique, blood is withdrawn from an athlete before a competition, and then is injected into his body again when he needs an extra boost. This can also be done with another person's blood.

Based on the analysis of the French anti-doping laboratory at Chatenay-Malabry, Vinokourov apparently used the blood of a compatible donor as two types of blood cells were found in his sample, France's sports daily L'Equipe reported on its Web site Tuesday.

If the positive test is confirmed by the so-called B sample, Vinokourov -- widely considered a favorite to win the Tour before the race started -- faces a ban from the sport of at least two years.

After the revelations, the Swiss-based Astana team announced it was pulling all its riders, including Klöden, out of the Tour.