AMERICAN Jessica Hardy, one of Leisel Jones' and Libby Trickett's genuine rivals at the Beijing Olympics, has tested positive to a banned substance.

The former world record-holder's A and B sample from the recent US Olympic trials have tested positive, according to reports from the US.

Typically, a first-time doping offence results in a two-year competitive ban, although Hardy could appeal to the American Arbitration Association and the Court of Arbitration for Sport.

The 50-metre breaststroke world champion was expected to be one of the few swimmers capable of derailing Jones in the 100 metres. Hardy, 21, is the only other person besides Jones to have held the world record in the event in the past five years.

The Californian's best time of one minute 6.20 seconds is a second outside Jones' world mark, and her 24.48 in the 50 metres at the US trials thrust her into medal contention in the one-lap dash — an event in which Trickett is the hot favourite to collect the title.

Hardy's agent, Evan Morgenstein, said Hardy told him in a phone conversation: "I never did anything wrong. I never cheated."

Morgenstein said he'd heard conflicting results from Hardy's tests, though he didn't have any details. "I'm very, very concerned about the confusion of her test coming up positive-negative-positive," Morgenstein said.

"She's the one person I would never believe would do anything, anything to cheat."

Hardy admitted during the swimming trials that she had been surprised by her performances. "I don't think if you had told me a month ago that I would make it in all three of these events that I would have believed you," Hardy said after qualifying for 50 metres freestyle, 4 x 100 relay and 100 breaststroke. "I'm expecting good things for sure."
AAP