The 23-year-old from Virginia faces a two-year suspension from the sport and an additional ban from the London 2012 Olympics after his reported admission and a statement from his lawyer that he took an over-the counter supplement containing the banned steroid DHEA (Dehydroepiandrosterone), which is a steroids precursor.

According to the release from lawyer Howard Jacobs, Merritt used an over-the-counter male enhancement product that contained substances that caused him to fail three successive tests between October and January.

Merritt said he hopes his family, friends and sponsors will forgive him for making "a foolish, immature and egotistical mistake".

He said he will not compete until the case has been decided.

USA Track and Field (USATF) chief executive Doug Logan issued a strongly-worded statement, criticising Merritt.

"We understand that Mr. Merritt's case is still ongoing with the US Anti-Doping Agency (USADA), and USATF awaits USADA's decision on the case," Logan said.

"Any professional athlete in this sport knows that they are solely responsible for anything that goes into their bodies.

"For Mr Merritt to claim inadvertent use of a banned substance due to the ingestion of over-the-counter supplements brings shame to himself and his team-mates."

The US has been hit by a series of doping scandals over the past decade involving some of the sport's biggest names, including former world 100m record holder Tim Montgomery and Marion Jones, who was stripped of the five Olympic medals, including three gold, she won at Sydney in 2000 after she admitted having used performance-enhancing drugs.

Logan said: "Thanks to his selfish actions, he has done damage to our efforts to fight the plague of performance-enhancing drugs in our sport.

"Mr Merritt has been an integral part of Team USA and the sport in this country.

"He has now put his entire career under a cloud.

"Personally, I am disgusted by this entire episode."

Merritt burst onto the scene in 2004 when he won the world junior 400m title.

He claimed the silver medal at the 2007 World Championships in Osaka, where he was part of the US team that won the 4x400m relay.



Merritt romped to a sensational victory at the Olympics in Beijing in 2008 when he beaten American team-mate Jeremy Wariner by 0.99sec, the largest winning margin in the 112-year history of the Games, clocking 43.75sec, making him the fifth fastest one-lap runner ever.

He underlined his domination last year in Berlin when he again beat Wariner to win the world 400m gold medal and helped the US retain their relay title.

Under International Olympic Committee (IOC) rules any athlete who tests positive for banned drugs is automatically suspended from the next Games.

Merritt claimed that he had made an error in testing positive.

"To know that I’ve tested positive as a result of product that I used for personal reasons is extremely difficult to wrap my hands around,” Merritt said in the release.

"Any penalty that I may receive for my action will not overshadow the embarrassment and humiliation that I feel inside."

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