Mark Zuckerberg announces he has backed out of a cage fight with Elon Musk, saying in a social media post that the Tesla boss is “not serious”.

The rival billionaires apparently agreed to a fight in June, when Musk tweeted that he was “ready for a cage fight.”

Zuckerberg, who runs Facebook and Instagram, took a screenshot of Musk’s tweet, replying “send me the address.”

However, he tweeted on Sunday on social media platform Threads: “I think we can all agree that Elon is not serious and it’s time to move on. I mentioned the actual date. Dana White (UFC boss) he offered to make this a legitimate competition for charity. Elon doesn’t want to confirm once, then says he needs surgery, and now he’s asking for a practice round in my backyard instead. If Elon ever gets serious about a real and official date, he knows where to find me. Otherwise, it’s time to move on. I will focus on meeting people who take sports seriously.”

Musk, the owner of Twitter, which he renamed X, suggested the fight would take place in an “epic location” in Italy.

He presented broadcast options and an antique setting for the proposed event, claiming to have spoken to Italian Prime Minister Giorgia Maloni.

Tensions have been brewing between the two billionaires’ companies since Zuckerberg’s Meta launched Threads, a text messaging app, in July. Twitter sent Zuckerberg a notice after the launch, saying Meta had “misappropriated Twitter’s trade secrets and other intellectual property.”

Zuckerberg studies mixed martial arts and posted a message about completing his first jiu-jitsu tournament earlier this year.

Last week, Musk said he was training for the fight by lifting weights. He wrote on X: “I don’t have time to practice so I bring them to work.”