DENVER -- Olympic gold medalist Tyler Hamilton was suspended Monday from competitive cycling for two years for a blood-doping violation discovered at a race in September.

The independent American Arbitration Association-North American Court of Arbitration for Sport handed down the suspension.

Hamilton is eligible to return to competition April 17, 2007, but he forfeits all competitive results since Sept. 11, 2004, the day of the positive test at a race in Spain.

The test occurred after Hamilton won the time trial at the Athens Olympics.

Hamilton has denied doping allegations.

On his Web site, www.tylerhamilton.com, Hamilton has written an extensive denial and explanation of the charges. In it, he writes, "I would never risk my health or my wife’s health for the sake of racing. That just goes without saying."

News of Hamilton's suspension came the say day Lance Armstrong announced his retirement after this year's Tour de France.

"I have decided the Tour De France will be my last race as a professional cyclist," he said at a news conference Tuesday.

The 33-year-old Texan, who rides for the Discovery Channel team, said he wanted to spend more time with his family, especially his three children.

He thanked his teammates, his team manager Johann Bruyneel, family and friends for their support during his career.

Before Armstrong, no one had more than four straight or five overall Tour de France races. Armstrong's streak of six straight titles has made him a legend in the sport and an international celebrity.

Armstrong's announcement came as a prelude to the Tour de Georgia, a race he won last year. The six-day, 648-mile event begins Tuesday in Augusta.