Hamburg  - Former Tour de France winner Jan Ullrich said the question of whether he was ever guilty of doping would be answered in a book he intended to write.

"These questions are not that easy to answer. Such things will be written about in a book which I will write for my fans and also for myself," he was quoted as saying in the Bild am Sonntag newspaper.

The 1997 Tour winner said that he would give himself as much time as he needed to write the book.

Ullrich suggested in the interview that not everything had been above board during his career.

"I am not in a position to help those who still are unable to add one and one and to know what was going on in cycling," the 35-year-old said.

Ullrich remains bitter about his forced retirement in 2007. A year earlier he had been pulled from the Tour de France by his T-Mobile team over his alleged involvement with Spanish doping doctor Eufemiano Fuentes.

The German has always denied doping.

He said that he had a number of lucrative offers to write a tell- all book. "The offers went into the millions."

Ullrich, who now lives in Switzerland, criticised compatriots Joerg Jaksche and Patrik Sinkewitz, who gave evidence about doping in exchange for lenient treatment.

The two cyclists, who are currently working on their comebacks, said only the things that helped them, Ullrich said.

Ullrich welcomed his long-time rival Lance Armstrong's comeback.

"For cycling the focus that Armstrong receives will be very good," he said, adding that it would be difficult for the American though to return to his winning ways. dpa