LAS VEGAS — Jon Jones has denied using any performance-enhancing substances after a positive drug test knocked him out of the main event at Saturday's UFC 200.

The UFC interim light heavyweight champion broke into tears at a hastily arranged news conference Thursday, a day after his rematch with Daniel Cormier was cancelled.

"I would never take anything that would enhance my game," Jones said. "Being labeled as someone who would ever cheat, it hurts me more than anything I've ever been through in my career."

Jones' manager, Malki Kawa, said the fighter was informed of a possible PED violation by USADA, which administers the UFC's anti-drug policy. Jones' backup sample will be tested by a lab in Utah, and Kawa hopes to get the results later Thursday, although he has little hope the result will change.

Jones and Kawa declined to name the substance for which Jones was flagged, although Kawa said it "could be" related to a nutritional supplement.

Jones said he "can't even pronounce it. I've never even heard of it."

The long-reigning champion briefly left the stage at his news conference after being overcome with emotion.

"I just try to stay optimistic," he said. "I feel like I've put in a lot of work to get back to this point, and I feel like I have to re-climb a ladder."

Jones said he has been taking the same supplements for most of his career, and he has no idea why his June 16 test would yield a violation after he passed seven other doping tests this year. Although Jones had endured numerous public embarrassments due to his apparent use of recreational drugs, he has been a vocal opponent of performance-enhancing substances in mixed martial arts.

"You can say whatever you want about Jon over the years," Kawa said. "For the last year, he's done nothing but try his best to live his life right, to eat right, to do the right things, and obviously not to be in this type of predicament. ... He didn't cheat at all."

Although UFC President Dana White still is attempting to book a late replacement fight for Cormier, Brock Lesnar's heavyweight bout with knockout artist Mark Hunt is UFC 200's new main event. While fans arrived at T-Mobile Arena to watch open workouts for Hunt and Lesnar, workers tore down oversized posters of Jones and Cormier on the side of the new building.

The star-studded pay-per-view card still features two title fights and the return of Lesnar, the professional wrestling star taking his first MMA bout in 4 1/2 years. Lesnar, considered the biggest pay-per-view star in the sport's history, also was the headliner at UFC 100 in 2009.

"I feel a little bad for (Cormier)," Lesnar said. "Guys go hard. They go through training camps and put lots of time in, and that's where D.C. really gets the short end of the stick. It's really unprofessional of anybody of this calibre when something like that happens."

Jones cried openly when asked what he would say to Cormier, his longtime rival and frequent verbal sparring partner.

"I know this fight meant a lot to him," Jones said. "The fight meant a lot to me. ... I know some good will come from this, but right now it's hard to see it."

While Cormier likely will lose a significant amount of money even if he gets a late matchup, Lesnar and Hunt will get bigger paychecks from the UFC's biggest show of the summer.

"It's unfortunate. It's unprofessional," Lesnar said. "Merry Christmas to Brock Lesnar."

Jones (22-1) is widely considered the world's top pound-for-pound mixed martial artist, winning the 205-pound title in 2011 and defending it eight times. But he has endured numerous troubles of his own making in recent years.

He has failed drug tests around two of his last three fights. He tested positive for cocaine use shortly before beating Cormier in their first meeting in January 2015, but was allowed to fight because the detected metabolite was not banned for out-of-competition use by the Nevada Athletic Commission.

A few months later, Jones was suspended by the UFC and had his title stripped due to his involvement in a hit-and-run accident in Albuquerque, New Mexico, where the upstate New York native lives and trains.

Jones is still on probation from that incident, but Kawa doesn't believe a positive doping test would impact it.

Cormier won the light heavyweight title during Jones' UFC suspension, which was lifted in October 2015. After Cormier pulled out of their first scheduled rematch with a foot injury, Jones returned in April with a victory over Ovince Saint Preux.

Jones, who turns 29 years old later this month, realizes he could face a multiyear suspension for a doping violation after USADA and Nevada officials adjudicate his case. He has fought just four times since September 2013.

"If I do have to sit out for two years, I'll definitely be back," Jones said. "I'm already thinking about the good that can happen. I try to stay optimistic. At the end of the day, I'm a fighter, and even though I may seem broken up here, I'm not broken. I'm just really upset."