(Reuters) - Lance Armstrong's success pushed Jan Ullrich to resume doping at the start of the last decade to give the German any chance of competing against his American rival, the 1997 Tour de France winner's mentor said on Friday.

Under Rudy Pevenage's guidance, Ullrich won the race 15 years ago but finished second to Armstrong three times between 2000-03. The American won the race seven times in a row from 1999.

"Did we have a choice? After the Festina scandal in 1998, we had stopped everything at (team) Telekom. No substances, no preparation, nothing!" Rudy Pevenage, who was implicated in the Operacion Puerto blood-doping scandal that broke in 2006, told French sports daily L'Equipe.

"We worked like this until 2001, believing that our rivals were doing the same. But Armstrong and U.S. Postal made us wonder. We were seeing that nothing was true with them. We were seeing that Armstrong had become superhuman," the Belgian added.

"What could we do? Let him play while no control could get him? We tried to find the recipe. The same recipe as Armstrong. Today we finally can say that we were all the victims of Lance Armstrong and (U.S. Postal manager) Johan Bruyneel."

The United States Anti-Doping Agency (USADA) released an extensive report on Wednesday saying it had "undeniable evidence" that Armstrong was one of the ringleaders of an elaborate doping program that took him to the top of world cycling.

The report was published six weeks after the USADA stripped Armstrong of his seven Tour de France victories and banned the American for life after he opted not to contest their claim that the Texan had doped throughout his career.

Two years ago, Pevenage admitted that he organized Ullrich's trips to see Eufemiano Fuentes, the doctor at the heart of the Operacion Puerto doping case.

Ullrich was found guilty of doping by the Court of Arbitration for Sport (CAS) in February for his role in the scandal.

He was banned for two years and CAS annulled his results from 2005 until his retirement two years later.

(Reporting by Julien Pretot; Editing by John O'Brien)