LONDON (AP) - Olympic 100-meter champion Justin Gatlin will have his appeal of a four-year doping ban heard next month by the Court of Arbitration for Sport.

The hearing will take place May 28-29. CAS, which is based in Lausanne, Switzerland, did not say where the hearing will be held.

Gatlin filed the appeal with sport's highest court Feb. 28, seeking to void the first of his two doping violations so he can compete at this year's Beijing Olympics. The hearing will be early enough to potentially allow Gatlin to race at the U.S. Olympic trials June 27-July 6 in Eugene, Ore.

Gatlin has maintained that he never knowingly took a performance-enhancing drug.

A U.S. arbitration panel reduced Gatlin's suspension to four years from a possible eight-year ban, but that still would prevent him from competing in China.

Gatlin tested positive for excessive testosterone at the Kansas Relays in 2006, his second doping violation. His attorney, Maurice Suh, contends his first doping violation, in 2001, should be rescinded because it involved a medicine that Gatlin - then 19 - was taking for attention deficit disorder.