Olympic decathlon champion Bryan Clay has withdrawn from the athletics World Championships with a minor knee injury.

"I feel that I would be at less than my best," the American said in a statement released by his manager Paul Doyle. "I want to win medals every time I compete and based on the way my knee has been over the past six weeks, I feel that I would not be at top form," the 31-year-old said.

The championships begin next Saturday in Daegu.

Clay fell in the decathlon 110 metres at the U.S. world trials in June and withdrew from the competition. He later developed tendonitis in his right knee.

His goal now is to prepare for London where he hopes to become the first decathlete to win three Olympic medals. Clay took silver in Athens in 2004 and gold in Beijing in 2008.

The Americans will still field a powerful decathlon team in Daegu led by world champion Trey Hardee and 2011 world leader Ashton Eaton.

Reuters