Jessica Hardy has agreed to withdraw from the US Olympic team after testing positive for a banned stimulant.

The US Anti-Doping Agency (USADA) announced on Friday Hardy tested positive for clenbuterol at the US Olympic trials.

Hardy, a 21-year-old from Long Beach, California, could have contested the finding but chose not to in the "best interests of the team," according to the USADA.

"While it is an unfortunate circumstance for an Olympian to come this far only to lose a coveted position on the Olympic team, Ms Hardy is working expediently and agreeably to resolve the situation with as little impact to the US Olympic team as possible," USADA chief executive Travis T Tygart said.

"While some might have chosen to exhaust their legal options to try to force their way into the Games, Jessica instead chose to put her team's interests ahead of her own."

Hardy had earned an Olympic berth by winning the women's 100-metre breaststroke final at the Olympic trials. She was expected to swim in four events in Beijing - the 100m breaststroke, the 50m freestyle, 4x100m medley relay and 4x100m freestyle relay.