NEW YORK (AP) -- Amir Khan's promoter has canceled the British boxer's fight against Lamont Peterson because of the American's failed drug test. Golden Boy Promotions announced on its website that the May 19 rematch for the WBA and IBF junior welterweight belts was called off. The statement Wednesday cited Peterson's positive doping test and the Nevada Athletic Commission's inability to hold a hearing on Peterson's licensing before Tuesday. The rematch in Las Vegas had been in doubt since Tuesday, when Athletic Commission executive Keith Kizer said a urine test in March found unacceptably high levels of synthetic testosterone in Peterson's system. "First of all I'm disappointed because I trained very hard for this fight," Khan told British broadcaster Sky Sports News on Thursday. "... . I really, really wanted to win my titles back and have the fight. But the truth's come out now and it just proves that Lamont Peterson was a cheat really." Peterson (30-1-1, 15 KOs), of Washington, defeated Khan in a disputed split decision on Dec. 10 in the U.S. capital to become the WBA and IBF junior welterweight champion. Khan (26-2, 18 KOs) was granted a rematch after complaining about the referee's decision to deduct him two points for pushing. He also was upset by the presence of an unauthorized man at ringside who was seen distracting an official. Peterson's publicist, Andre Johnson, told Sky Sports News that the American fighter had done nothing wrong and would fight to clear his name. "Lamont Peterson has been boxing for 18 years. In 18 years, barring this incident, he's never tested positive for anything," Johnson said. "After this incident, three other tests were taken that he tested negative for. "We're going to get to the bottom of this and do everything in our power to clear Lamont's name. Lamont will be fighting very soon." Two tests of Peterson's urine samples by the Las Vegas-based Voluntary Anti-Doping Association reached the same positive finding, according to a report Kizer said he received Monday from Dr. Margaret Goodman, VADA chief executive and a former ringside physician. Washington, D.C.-based attorney Jeff Fried told Nevada's boxing regulators that Peterson's failed doping test stemmed from an "inadvertent" failure to disclose medical treatment last November for low testosterone levels. In a letter obtained Tuesday by The Associated Press, Fried told the Athletic Commission that Peterson's doctor determined that a one-time "therapeutic" treatment "would not produce a significant enhancement of athletic performance." Richard Schaefer, chief executive of Golden Boy, said he hopes Khan will be given back his WBA and IBF titles. "We are obviously going to ask the sanctioning organizations, the World Boxing Association and the International Boxing Federation, to rule this fight a no-contest and therefore give back the belts to Amir Khan -- where they belong," Schaefer told Sky Sports News. Johnson maintained Peterson was clean. "Lamont did nothing wrong. He's not a doper. He's not a cheater. He's distraught. He wanted to clear his name and do what he was born to do -- fight," the fighter's publicist said. "Mark my words: Lamont Peterson is a man of tremendous character -- he's a fighter. We will fight to get the truth."