Brett Okamoto explains that due to Cody Garbrandt's injury, Dana White announces that an interim middleweight title fight between Yoel Romero and Robert Whittaker will co-headline UFC 213. (0:59)

The UFC has made significant changes to its UFC 213 pay-per-view event on July 8 in Las Vegas.

UFC president Dana White told ESPN.com on Tuesday that a bantamweight title fight between Cody Garbrandt and TJ Dillashaw has been officially called off, due to a Garbrandt back injury.

According to White, Dillashaw (14-3) will be rebooked to a flyweight title fight against 10-time defending champion Demetrious Johnson in August. Johnson, though, said later Tuesday that he's not interested in such a fight.

Meanwhile, a newly announced interim middleweight title fight featuring Yoel Romero and Robert Whittaker will serve as the UFC 213 co-main event, White said. The card will be headlined by female bantamweight champion Amanda Nunes (14-4), who is defending her title against Valentina Shevchenko (14-2).

White told ESPN.com he decided to create an interim 185-pound title after speaking to the division's current champion, Michael Bisping, on Tuesday. Bisping (30-7) hasn't defended his title since October and is currently sidelined with a knee injury.

The changes to UFC 213 come after weeks of speculation on Garbrandt's health. Earlier this month, the UFC sent the 25-year-old champion to a stem cell specialist in Germany and had hoped he would be able to remain on the card. Ultimately, Garbrandt needed more time.

A back injury to Cody Garbrandt, above, has forced the cancellation of his scheduled UFC 213 bantamweight title fight against TJ Dillashaw. An interim middleweight title fight featuring Yoel Romero and Robert Whittaker will serve as the co-main event. AP Photo/John Locher

"After his last round of treatment in Germany, they told him he'd need four weeks to rest," White said. "That would have put him two weeks out from the fight.

"With Cody out, we're going to make T.J. versus Mighty Mouse [Johnson]. That's the plan."

Johnson (26-2-1) is one title defense away from breaking the UFC's all-time record of 10 consecutive title defenses. No official date has been set for his next title defense, but the UFC has looked at headlining a PPV event with Johnson on Aug. 19 in Seattle. Johnson fights out of Kirkland, Washington.

Romero (12-1) is riding a seven-fight win streak and coming off a flying knee knockout over Chris Weidman in November. Whittaker (18-4) has won six in a row.

UFC 213 will take place inside T-Mobile Arena, during the promotion's International Fight Week. The Ultimate Fighter 25 Finale is scheduled on July 7 at the same venue.