COLORADO SPRINGS, Colo. (AP) _ Olympic champion cyclist Tyler Hamilton's appeal of a two-year suspension for blood doping was rejected by the Court of Arbitration for Sport, the U.S. Anti-Doping Agency said Saturday.

Considered a possible successor to retired seven-time Tour de France champion Lance Armstrong, Hamilton has denied any doping violation and has criticized the testing methods of cycling's international governing body. He was suspended for two years on April 18 by the independent American Arbitration Association.

The Swiss-based CAS held 12 hours of hearings on the case in Denver last month.

Hamilton's case was the first based on a test designed to detect the presence of someone else's red blood cells in a sample. A blood transfusion can increase endurance by providing extra oxygen-carrying red blood cells to muscles.

``USADA has met its burden of proof by demonstrating the HBT test conducted by the Lausanne Laboratory was in accordance with the scientific community's practice and procedures,'' a news release said. The three-member panel unanimously confirmed the ABA finding.

Terry Madden, CEO of the USADA, said it had considered all theoretical explanations for the positive test, including an extortion plot by a fan of another team.

``The panel considered each of the excuses and found each to be completely without merit. It is sad that Mr. Hamilton resorted to conspiracy theories rather than just accept the consequences of his doping,'' said Madden.

Hamilton won't be able to race competitively until April 2007, when he would be 36 years old.

Hamilton tested positive during the Spanish Vuelta in September 2004, a month after he won the time trial gold medal at the Athens Olympics.

His initial blood sample in Athens also tested positive but that case was dropped because his backup specimen was mistakenly frozen and could not be analyzed.