Sprinter Tyson Gay has accepted a one-year ban and a loss of results dating back to July 2012 after testing positive for a prohibited substance, the United States Anti-Doping Agency has announced.

The 31-year-old American, a former world champion over 100m and 200m and the second fastest man in history, tested positive for the presence of an "exogenous androgenic anabolic steroid and/or its metabolites" following two out-of-competition and one in-competition tests last year.

Gay accepted a one-year period of ineligibility which began on 23 June, 2013, the same day his sample was collected at the USA Outdoor Track & Field Championships.

After electing to cooperate with USADA's anti-doping investigations, Gay was eligible for a reduction of the standard two-year sanction. His suspension is therefore reduced by 50 per cent, while it is also backdated to June 2013, meaning he will be eligible to return to competition next month.

As part of his forfeiture of results, Gay has already returned the silver medal he won as part of the US team in the men's 4x100m relay at the 2012 London Olympics.

A USADA statement read: "USADA announced today that Tyson Gay of Winter Garden, Fla., an athlete in the sport of track & field, has tested positive for a prohibited substance and accepted a loss of results dating back to July 15, 2012 and a one-year suspension for his anti-doping rule violation.

"Gay, 31, tested positive for the presence of an exogenous androgenic anabolic steroid and/or its metabolites which was confirmed by CIR (GC/C/IRMS) analysis, as the result of two out-of-competition and one in-competition urine samples collected by both USADA and the International Association of Athletic Federations (IAAF).

"Since all three samples were tested in short succession prior to notification of the first positive result, the three adverse analytical findings, under the rules, are treated as one offense.

"Upon receiving notification of his positive tests from USADA, Gay voluntarily removed himself from all competition prior to the 2013 World Championships and has not competed since that time.

"On the same day that Gay was notified of his positive test result, he agreed to assist USADA in its investigation of the circumstances of his positive tests. Gay provided substantial assistance as outlined in the WADA Code including being interviewed on several occasions by USADA and providing all of the products he was using at the time of his positive tests."