"We will take a team to Beijing that we are committed to ensuring is a clean team," U.S. Olympic Committee (USOC) chief executive Jim Scherr said in a conference call to mark next week's one-year countdown to the Games.

"I'm confident, slash hopeful," USOC chairman Peter Ueberroth said when asked if he believed Games organisers could avoid having the Olympics turn into two weeks of doping announcements.

Ueberroth, who returned to head the USOC after organising the 1984 Los Angeles Games, said recent doping scandals have led to "a low point for sports".

But he and Scherr said the United States would work hard over the next year to ensure it fielded a drug-free team.

"The United States Olympic Committee is forging additional activities in that field," Ueberroth said. "They tend toward more science and more effective deterrents.

"We are ramping up our efforts to support USADA (United States Anti-Doping Agency) and to support all of our athletes in ensuring we field a clean team in Beijing and beyond," Scherr added.

"We're dedicated to this effort," Scherr said. "I do not believe the Games will devolve into a question by the American public on whether or not athletes are competing fairly and cleanly."

Sarah Hammer, the world track cycling champion, said doping scandals in this year's Tour de France unfairly tainted the entire sport.

"It's kind of starting to tarnish everything I worked hard for because we're all getting grouped into it," Hammer said.

"I also believe we need these positive tests and we need to start catching these people before we can clean up the sport for good. It's got to go down before it's going up again."

Three riders, including pre-race favourite Alexander Vinokourov, tested positive for doping during the Tour de France, sullying the image of the sport's biggest stage race.

Danish rider Michael Rasmussen was also sacked during the Tour by his Rabobank team for lying about his training whereabouts and was forced to leave the race when he was in the lead.