Billionaire SpaceX, Tesla and X owner Elon Musk says he plans to sue Apple for not featuring X and its Grok artificial intelligence chatbot app in its top recommended apps in its App Store.

Musk posted the comments on X late Monday, saying, “Hey @Apple App Store, why do you refuse to put either X or Grok in your ‘Must Have’ section when X is the #1 news app in the world and Grok is #5 among all apps? Are you playing politics? What gives? Inquiring minds want to know.”

Grok is owned by Musk’s artificial intelligence startup xAI.

Musk went on to say that “Apple is behaving in a manner that makes it impossible for any AI company besides OpenAI to reach #1 in the App Store, which is an unequivocal antitrust violation. xAI will take immediate legal action.”

He gave no further details.

There was no immediate comment from Apple, which has faced various allegations of antitrust violations in recent years.

A federal judge recently found that Apple violated a court injunction in an antitrust case filed by Fortnite maker Epic Games.

Regulators of the 27-nation European Union fined Apple 500 million euros in April for breaking competition rules by preventing app makers from pointing users to cheaper options outside its App Store.

Last year, the EU fined the U.S. tech giant nearly $2 billion for unfairly favoring its own music streaming service by forbidding rivals like Spotify from telling users how they could pay for cheaper subscriptions outside of iPhone apps.

As of early Tuesday, the top app in Apple’s App Store was TikTok, followed by Tinder, Duolingo, YouTube and Bumble. Open AI’s ChatGPT was ranked 7th.