LAS VEGAS -- Interim UFC light heavyweight champion Jon Jones has been pulled from his title unification bout against Daniel Cormier at UFC 200 on Saturday, after the U.S. Anti-Doping Agency informed Jones of a potential doping violation Wednesday.
UFC president Dana White announced the move Wednesday during an impromptu news conference at the MGM Grand.
Jones tested positive for a banned substance in an out-of-competition sample taken June 16 by USADA, said Jeff Novitzky, UFC's vice president of athlete health and performance. USADA administers UFC's anti-drug policy.
"It is important to note that under the UFC anti-doping policy, there's a full, fair legal-review process that is afforded to all athletes before any sanctions are imposed," Novitzky said.
Novitzky added that there wasn't time for a "full review before the scheduled bout."
White said he has not spoken to Jones yet and that he wasn't aware whether the substance in question was a performance-enhancing drug.
A heavyweight fight between Brock Lesnar and Mark Hunt will now headline UFC 200, which takes place Saturday at T-Mobile Arena.
Jones has the right to appeal any positive test. He has never tested positive for performance-enhancing drugs but did test positive for traces of cocaine before a fight against Cormier in January 2015.
Jones also served a suspension from April to October after his involvement in a hit-and-run accident.
He is scheduled to address the media Thursday at 11:30 a.m. ET at the MGM Grand.
Under UFC's anti-doping program, which went into effect last July, a positive test for a performance-enhancing drug carries a standard two-year suspension.
In an interview with ESPN last week, Jones had expressed hope he could turn his legacy into a positive one.
"I want to show the world that you can be down but never out," Jones said. "I want to be a story where someone risked losing so much but ultimately turned everything around. A lot of times you hear these stories about athletes who ruined their career and they go away and no one knows what happened to them or they're bankrupt or they end up in jail. They just ruined a great career. I want to be one of the few stories you hear where I was ruining things but ultimately turned things around and became a hero. That's my vision for the way my story is going to play out."
White said he would like to find Cormier, the defending light heavyweight champion, a new opponent, but that would be difficult because of the timing.
"When you have the biggest, baddest fight card ever assembled, you know, it doesn't sting as bad when you lose a fight," White said. "But it stings real bad for Daniel Cormier. This is devastating to him, his family, and I'd like for him to fight another guy."
Cormier appeared next to White during the news conference.
"I've trained hard and long," Cormier said. "If anybody would fight, I would fight. Why not? I understand the difficult task it would be to find me a fight on two days. I'm willing to fight up, put on some weight, 225, 220 [pounds]. I'll fight. It doesn't matter. I just can't fight a really big guy, because I've been shrinking my body."
Cormier said he would put in the effort and would accept a new fight if UFC could find one that "made sense."
"I've worked really hard to prepare for this," Cormier said. "You take care of what you need to take care of. That's what I did. More than anything, it's really disappointing."
Cormier said having USADA as UFC's partner in the administration of drug testing "changes a lot of things" and that UFC made a conscious decision to bring in USADA.
"They didn't have to do this," Cormier said. "They decided to clean up the sport. You're going to have casualties."
Cormier said he got a bad feeling in the pit of his stomach when White texted him Wednesday, asking him whether he could make it to the news conference.
"This guy always gives me good news," Cormier said of White. "You know, this guy calls you with a seven-figure check -- 'dude, you're rich now' -- you know, he calls you with good news. And the mood didn't feel very good. It was scary. So I came here, and I was actually early. It's probably the first time I've ever been early. I needed to know. But he's usually the good-news guy. And today he had to give me some pretty bad news."
Information from ESPN senior writer Arash Markazi and The Associated Press was used in this report.