Gay, the American record-holder in the 100, will not compete in the world championships next month in Moscow after he said he was notified by the
"I don't have a sabotage story," said Gay, who battled injuries in the last two
"I basically put my trust in someone and was let down," he added.
The 30-year-old sprinter said he will have his "B" sample tested soon to confirm the first test.
"I don't want to use certain words, to make it seem like an accident, because I know exactly what went on, but I can't discuss it right now," Gay said. "My career and my name have always been better than medals or records or anything like that. I've always wanted a clean name with anything. Unfortunately, I have to break this news, that I have a positive 'A' sample.
"I will take whatever punishment I get like a man. I do realize and respect what I put in my body and it is my responsibility. I'm going to be honest with USADA, about everything, everybody I've been with, every supplement I've ever taken, every company I've ever dealt with, everything."
Gay ran the fastest time in the world at the time for 100 meters, a wind-aided 9.68 seconds, in the 2008 U.S. Olympic trials but injured his hamstring in the 200 and was hobbled through the
He sustained a hip injury in 2011 that required surgery but recovered in time to finish second at the U.S. Olympic trials in 2012 and qualify for the London Olympics. He finished fourth in the Olympics, posting a time of 9.80, one-hundredth of a second behind bronze medalist
Gay, who holds the American 100 record at 9.69 seconds, would later win his first and only Olympic medal by taking part in the Americans' silver-medal effort in the 400-meter relay.