"It's something that happened," Young was quoted as saying on the Los Angeles Times website on Friday. "It's all past and it's something I don't want to talk about."

On Wednesday the newspaper alleged Young had tested positive for the anabolic steroid nandrolone in 1999, but had been subsequently cleared by the American federation and allowed to compete at the 2000 Sydney Olympics.

IAAF spokesman Nick Davies said on Friday the world governing body would attempt to get in touch with Young, who is scheduled to run for the U.S. 4x400 metres relay team at the weekend.

According to IAAF rules athletes can be banned if they admit "either orally in a verifiable manner or in writing" they had committed an offence in the previous six years.

Both the IAAF and USA Track & Field previously said they could not comment on the case after a Court of Arbitration for Sport ruling that the American federation did not have to release the names of five athletes who had competed in Sydney despite failing dope tests.

On Thursday, the International Olympic Committee urged the IAAF and USA Track & Field to pursue the newspaper allegations about Young.

Young won a gold medal in the 4x400 metres relay in Sydney after competing in an early round although not the final.