Elon Musk on Monday threatened legal action against Apple over alleged antitrust violations concerning the rankings of the Grok AI chatbot app, owned by his AI startup xAI.

“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,” Musk wrote in a post on his social media platform X.

Apple has yet to respond to request for comment.

“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?” Musk said in another post.

Last year, Apple partnered with OpenAI to integrate ChatGPT into its iPhone, iPad, Mac laptop, and desktop products. At that time, Musk warned, “If Apple integrates OpenAI at the OS level, then Apple devices will be banned at my companies. That is an unacceptable security violation.”

Before threatening legal action against Apple, Musk celebrated Grok surpassing Google as the fifth top free app on the App Store.

ChatGPT held the No. 1 spot among top free apps in the U.S. iOS store and was the only AI chatbot featured in Apple’s “Must-Have Apps” section.