Billionaire Elon Musk, who owns SpaceX, Tesla, and X, has announced his intention to sue Apple. This follows Apple’s decision not to feature X and its Grok artificial intelligence chatbot app in the top recommended apps section of its App Store.

Musk expressed his dissatisfaction on X late Monday, questioning why Apple does not include X or Grok in its “Must Have” section. He pointed out that X is the leading news app globally, and Grok ranks fifth among all apps. Musk questioned if Apple’s motives were political, asking for clarification.

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

Musk further accused Apple of obstructing competition, claiming it prevents any AI company, except OpenAI, from becoming number one in the App Store, which he described as a clear antitrust violation. He stated that xAI would promptly pursue 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.

The European Union previously fined Apple 500 million euros in April for violating competition rules by stopping app makers from directing users to cheaper alternatives outside its App Store.

Last year, the EU penalized the U.S. tech giant nearly $2 billion for giving preferential treatment to its own music streaming service. Apple had restricted competitors like Spotify from informing users about more affordable subscription options outside 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.