Kloeden, 38, won the 2000 Paris-Nice race and finished third in the Sydney Olympics road race in the same year.
He seldom talked to German media in the last years of his career, angered by what he said were false allegations of doping, and has been living in Switzerland.
Several retired fellow German riders including Erik Zabel and Jan Ullrich have since made full or partial doping admissions for a period when the use of banned substances was rampant in the sport.
Kloeden, however, who played mostly second fiddle to them in his career, always denied the claims.
"I have nothing to admit to," he told the Weserkurier newspaper.
He finished 30th in his 12th and last Tour this year.