Billionaires and social media business rivals Mark Zuckerberg and Elon Musk threw new online jabs at each other Sunday, with the Meta founder declaring the owner of X -- formerly known as Twitter -- was not treating a proposed charity cage match seriously.

"I think we can all agree Elon isn't serious and it's time to move on," Zuckerberg wrote on his Threads social platform.

"I offered a real date... Elon won't confirm a date, then says he needs surgery, and now asks to do a practice round in my backyard instead."

Musk quickly responded on X, the platform he bought last year that was previously called Twitter.

"Zuck is a chicken," Musk posted.

The Tesla boss said he would head to Silicon Valley Monday: "Can't wait to bang on his door tomorrow."

When an X user suggested Zuckerberg was getting cold feet about the match, Musk referred to a popular US fast food chain known for its chicken offerings.

"He can't eat at Chick-fil-A because that would be cannibalism," Musk posted.

The two tech titans have gone back and forth on social media about fighting each other in a much-hyped charity match.

Musk said Friday the fight would take place in Italy, as authorities there confirmed talks about hosting a "great charity event."

"I spoke to the PM of Italy and Minister of Culture," Musk wrote, referring to Italian Prime Minister Giorgia Meloni. "They have agreed on an epic location."

In response, Zuckerberg posted a photo of himself shirtless and pinning down an opponent in his "backyard octagon."

A martial arts enthusiast who has taken part in jiujitsu competitions, Zuckerberg said, "I love this sport and I've been ready to fight since the day Elon challenged me."

"If he ever agrees on an actual date, you'll hear it from me. Until then, please assume anything he says has not been agreed on."

Italian Culture Minister Gennaro Sangiuliano confirmed speaking to Musk about "how to organize a great charity event evoking history" but said any match "will not be held in Rome."

Sangiuliano said any event with Musk would raise "a huge sum, many millions of euros, (that) will be donated to two important Italian pediatric hospitals."

The two tech tycoons, who have occasionally jousted from afar, became direct competitors after Zuckerberg's Meta launched its Twitter-like Threads platform in early July.

Musk noted on Friday that he may need to undergo "minor surgery" to resolve a "problem with my right shoulder blade rubbing against my ribs."

"Recovery will only take a few months," he added.

The world's richest person has a titanium plate holding two vertebrae together but said Friday it is currently "not an issue."