The thought of Elon Musk challenging Mark Zuckerberg to a physical fight may be hard to fathom, but both tech CEOs are “dead serious” about duking it out in the ring, according to Ultimate Fighting Championship (UFC) President Dana White.

“I was talking to both Elon and Mark last night. Both guys are absolutely dead serious about this,” White said in an interview with TMZ Live on Thursday. “They both said, ‘Yea, we’ll do it.’ They both want to do it."

White made the statement after Zuckerberg and Musk apparently agreed to a “cage match” through posts on Instagram and Twitter.

White said he probably spent an “hour and half with both of them on the phone” on Wednesday night talking about the potential match.

“This would be the biggest fight ever in the history of the world,” he said. White expects the UFC-style cage match could generate at least three times more than the Floyd Mayweather Jr. vs. Connor McGregor bout in 2017, which drew an estimated $600 million in revenue.

“There’s no limit on what this thing can make,” White says. Any money raised would go to charity, though it would be a publicity boon for White and the UFC.

But it sounds like both Musk and Zuckerberg will need to commit to the fight, beyond one day of merely entertaining the idea. “If they really want to do it, and they’re serious, and we can figure it out, figure out a way to pull this off, I would absolutely, positively do this,” White said, later adding: “This is early stages, we’ll see how it plays out.

On how much the fight will cost for the public to watch, White said, “probably a hundred bucks.”

In the meantime, a few offshore sportsbooks have released odds for the potential fight, with one slightly favoring Musk, the other heavily favoring Zuckerberg, according to Casino.org.

The potential fight comes as Zuckerberg plans on launching a rival to Elon Musk’s Twitter, reportedly dubbed Threads. Over the years, Musk has also feuded with Facebook’s founder on AI and privacy matters, so both tech CEOs may have a real dislike for each other.

In terms of fighting skills, the 39-year-old Zuckerberg, who’s been listed at 5 foot 7 inches, has been training with professional fighters in Brazilian jiu jitsu and boasting about it in his posts on Facebook and Instagram. “Competed in my first jiu jitsu tournament and won some medals,” he wrote last month, although Zuckerberg also lost one match.

Musk’s fighting skills remain less clear. But according to White, the Tesla CEO has also trained in martial arts, including jiu jitsu. In addition, Musk—who stands at 6 feet and 1 inches and is 51 years old—has previously said he’s gotten into plenty of fights growing up in South Africa.