Jon Jones Breaks Down in Tears ... I'm Not a Cheater

Jon Jones wept openly while insisting he never knowingly cheated by taking performance-enhancing drugs, and vowed to return to the UFC.

Surprisingly, Jones opened his news conference by apologizing to Daniel Cormier for ruining their long-awaited rematch that was supposed to go down Saturday at UFC 200.

Jones says he "can't even pronounce" the drug the UFC says showed up in a blood test he took in June. He would not say the drug by name, but said he has no idea how it ended up in his system.

Jones says he will "go through the process" and try to find out what caused the dirty test. He admitted to taking a few supplements, but said he didn't think they were performance-enhancing.

At one point, he got so emotional, he walked out of the room. He returned several minutes later, but then couldn't hold back tears when he was asked if he'd spoken to Cormier.