Pearson rival Harper-Nelson cops ban

Australian Sally Pearson's long-time hurdles rival Dawn Harper-Nelson has been suspended for three months after testing positive to a banned substance.

American hurdler Dawn Harper-Nelson has been suspended after testing positive to a banned substance. (AAP)

Sally Pearson's long-time rival, American Dawn Harper-Nelson, has been suspended for three months after testing positive for a banned substance.

The US Anti-Doping Agency announced the sanction on Tuesday (Wednesday AEDT).

Harper-Nelson won gold in the 100m hurdles at the 2008 Beijing Games when Australian star Pearson took silver and claimed silver when Pearson triumphed four years later in London.

USADA says the 32-year-old Harper-Nelson tested positive for the prohibited substance hydrochlorothiazide and related metabolites in an out-of-competition sample.

She told USADA it was caused by blood pressure medication prescribed by a physician to treat hypertension.

In a statement posted on her Twitter account, Harper-Nelson said she has learned "a valuable lesson and hope my mistake will serve as a reminder to all athletes to be diligent in thoroughly checking any and all prescribed medications."

Her period of ineligibility started December 1.