Tearful former double sprint world champion Tyson Gay said yesterday he had tested positive for a substance he could not identify and was pulling out of next month’s World Championships in Moscow.

Gay, who had the year’s fastest 100 metres time of 9.75 seconds, told two reporters in a telephone conference call he was notified by the US Anti-Doping Agency (USADA) on Friday that his A sample from an out-of-competition test on May 16 had returned a positive.

“I don’t have a sabotage story. I don’t have lies... I basically put my trust in someone and I was let down,” said Gay, who added he had never knowingly taken a performance-enhancing drug.

“I made a mistake,” added the 30-year-old sprinter from his training base in Amsterdam.

“I am pulling out of Monaco (Diamond League meeting on Friday) and the worlds.”

Gay, the world 100 and 200 champion in 2007, said he could not divulge the substance or how the positive occurred.

“I am not allowed to talk about those things right now.

“I know exactly what went on, but I can’t discuss it right now,” he added.

“I hope I am able to run again. But I will take whatever punishment I get like a man.”