Michael Phelps swims during his heat in the men's 200m butterfly at the U.S. Olympic Swimming Trials in Omaha, Nebraska in this July 1, 2008.

Michael Phelps of the U.S. listens to the national anthem during the medal presentation ceremony after the men's 4x100m freestyle relay swimming final at the National Aquatics Center during the Beijing 2008.

BEIJING, Feb. 2 (Xinhuanet) -- Olympic gold medalist Michael Phelps issued an apology for his "regrettable" behavior Sunday after a photo showing him smoking a marijuana pipe was published.

"I engaged in behavior which was regrettable and demonstrated bad judgment," Phelps said in the statement released by one of his agents.

"I'm 23 years old and despite the successes I've had in the pool, I acted in a youthful and inappropriate way, not in a manner people have come to expect from me. For this, I am sorry. I promise my fans and the public it will not happen again."

Though Phelps will not face any sanction from anti-doping authorities for the apparent drug use because marijuana is only prohibited during competition, the U.S. Olympic Committee immediately released a statement chiding Phelps for failing to "fulfil his responsibilities" as a role model and describing Phelps's behavior as "disappointing."

"Michael is a role model, and he is well aware of the responsibilities and accountability that come with setting a positive example for others, particularly young people," the committee said. "In this instance, regrettably, he failed to fulfill those responsibilities."

"That said, we realize that none among us is perfect. We hope that Michael can learn from this incident and move forward in a positive way."

Phelps, in his statement, promised there would be no repeat.

"For this, I am sorry. I promise my fans and the public - it will not happen again."

Phelps won a record eight gold medals at the 2008 Summer Olympics in Beijing, China, four years after he won six gold medals at the Summer Olympics in Athens, Greece.