
In a statement USADA said that Floyd Landis committed a doping violation during the 2006 Tour de France.
Landis' last appeal is to the Court of Arbitration for Sport.
The US arbitration panel found that Landis, who tested positive during his Tour victory had been guilty of doping in that his doping sample was found to contain traces of a banned substance, synthetic testosterone.
"Following a nine-day evidentiary hearing and a lengthy post- hearing review of all the evidence and testimony submitted, the majority of the independent panel of arbitrators from the American Arbitration Association (AAA)/North American Court of Arbitration for Sport (CAS) found that the sample provided by Landis after his Stage 17 victory was positive for exogenous testosterone.
"As a result of his doping violation, Landis received a two-year suspension and forfeits his first-place finish in the 2006 Tour de France and all related prize money," the statement said.
USADA Chief Executive Officer Travis Tygart welcomed the ruling.
"Today's ruling is a victory for all clean athletes and everyone who values fair and honest competition," he said. "This decision confirms for the overwhelming majority of American athletes who compete ethically that USADA is committed to protecting their right to participate on a drug-free playing field.
"This case is really just another sad example of the crisis of character which plagues some of today's athletes and undermines the honest achievements of all of those athletes who compete with integrity.
"Hopefully, some of the good that comes from this type of case is that other athletes who might be tempted to cheat will recognize that there is no honour in doping to win."
"Everyone on USADA's team operates on one fundamental principle: Do what is right," Tygart said.
"Here, despite the intense pressure applied by Mr. Landis and his high-priced legal and public relations team, we knew that doing what was right required staying the course and fulfilling our duty to clean athletes.
"USADA brought the case against Mr. Landis because, as the independent panel confirmed today, the scientific evidence established that he had committed a doping violation."
Landis countered that the agency failed to make its case against him.
"This ruling is a blow to athletes and cyclists everywhere," Landis said in a statement released by his attorney Maurice Suh. "For the panel to find in favour of USADA when, with respect to so many issues, USADA did not manage to prove even the most basic parts of their case, shows that this system is fundamentally flawed. I am innocent, and we proved I am innocent."
The case was the first ever public hearing by the USADA - something Landis himself insisted on after a ground-swell of support in the US - and was held at Pepperdine University School of Law in Malibu, California.
At the time of the hearing Landis, who had denied using a performance-enhancing substance, said he was offered a deal by USADA to get off with a light sentence if he provided doping evidence against a former teammate - seven-time Tour de France winner Lance Armstrong.
Armstrong has been accused of using performance-enhancing drugs by French newspapers but never tested positive for doping.
Landis is the first cyclist in the 103-year history of the Tour de France to lose his title after being found guilty of a doping offence although Danish winner Bjarne Ris earlier this year admitted that he doped with EPO when he won the race in 1996, but because his admission came too late, he could not be stripped of the title.//dpa