LOS ANGELES (AP) - Veteran UFC light heavyweight Chael Sonnen has failed a drug test, forcing him out of his bout with Vitor Belfort at UFC 175 in Las Vegas next month.
Sonnen said he tested positive for two banned substances in a random test last month. The three-time UFC title contender is likely to face a suspension by the Nevada Athletic Commission.
Sonnen attempted to defend himself Tuesday, claiming he took anastrozole and clomiphene as part of his move off testosterone replacement therapy, which was outlawed by Nevada regulators earlier this year. Sonnen had an exemption allowing his steroid use, but gave up TRT after it was banned.
''They changed the rules, and I've got to comply with the rules,'' Sonnen told Fox Sports, the UFC's television partner. ''However, there is a transition period (after dropping TRT), and I couldn't have been more open or more transparent.''
The 37-year-old Sonnen (28-14-1) said he plans to appeal the commission's decision next week, even though he acknowledged knowing the two substances were on the Nevada commission's banned list.
Sonnen said his doctor put him on the banned substances to bolster his natural testosterone production, which can be stunted by taking synthetic testosterone. He also believes he should be allowed to take the substances out of competition, even though they're banned precisely to prevent athletes from using them to gain an unfair advantage in preparation for an event.
''An athlete does not have to remain off of medication 365 days a year,'' Sonnen said. ''If they're asking me to choose between my health and my sport, that's not a choice I can make. I've got to choose health.''
UFC President Dana White blamed both the Nevada commission and Sonnen while addressing the failed test on Fox Sports. White spoke out against TRT earlier this year, shortly before the Nevada commission banned it and many other commissions followed suit.
''This thing has been bad since Day 1,'' White said. ''I wish that the commission had never let anybody use TRT, and when it went away, they didn't do a very good job of figuring out how to get these guys off it. When you get off it, you don't just go cold turkey.
''And it's Chael's fault, too, because Chael should have called the athletic commission and said, `This is what my doctor told me I need to do to come down off this stuff, so here's what I've been taking.'''
Sonnen had lost three of his past four fights heading into his July 5 bout with Belfort, another former TRT user. While never a champion, Sonnen is among the UFC's most prominent figures, serving as a studio analyst, commentator and reality show coach for the UFC's broadcast platforms while also continuing his fighting career.
Sonnen also had high levels of testosterone in his system after his thrilling loss to middleweight champion Anderson Silva at UFC 117 in Oakland, California, in 2010. He received a suspension for failing to get an exemption for TRT in California.
Sonnen's latest drug mishap is another bizarre turn for UFC 175, which has endured numerous changes and strange circumstances. Belfort only got a spot on the pay-per-view card at the Mandalay Bay Events Center when Wanderlei Silva skipped a drug test last month and dropped out of his scheduled bout with Sonnen, who harshly criticized Silva on television for missing the test.
Belfort used TRT for at least his last three fights, all won by spectacular knockout in his native Brazil. He dropped out of a scheduled fight with UFC middleweight champion Chris Weidman in late February on the same day the Nevada commission banned TRT.
Belfort says he has since stopped using steroids. He is scheduled to appear at a licensing hearing with the Nevada commission next week.
UFC 175 is headlined by Weidman's title defense against Lyoto Machida and bantamweight champion Ronda Rousey's fourth title defense against Alexis Davis.