Elon Musk is suing Microsoft-backed OpenAI and its CEO Sam Altman, among others, alleging they abandoned the company’s founding mission to develop artificial intelligence “for the benefit of humanity broadly.”

In a lawsuit filed on Thursday with a San Francisco court, Musk’s lawyers said the tech billionaire was approached in 2015 by Altman and OpenAI co-founder Greg Brockman and agreed to form a non-profit lab that would develop artificial general intelligence for the “benefit of humanity.”

A co-founder of OpenAI in 2015, Musk stepped down from the firm’s board in 2018, four years after saying that AI is “potentially more dangerous than nukes.”

“To this day, OpenAI, Inc.‘s website continues to profess that its charter is to ensure that AGI benefits all of humanity.’ In reality, however, OpenAI, Inc. has been transformed into a closed-source de facto subsidiary of the largest technology company in the world: Microsoft,” the lawsuit filing said.

Musk’s lawyers said in the lawsuit that OpenAI’s focus on maximizing profits for Microsoft breaks that agreement.

“Under its new Board, it is not just developing but is actually refining an AGI to maximize profits for Microsoft, rather than for the benefit of humanity,” the filing said.

OpenAI and Microsoft were not immediately available for comment.

Musk’s lawyers said the suit was submitted “to compel OpenAI to adhere to the Founding Agreement and return to its mission to develop AGI for the benefit of humanity, not to personally benefit the individual Defendants and the largest technology company in the world.”

The legal action pits two of the world’s most prominent tech leaders against each other at a time of extraordinary hype over the future of AI.

Since debuting in Nov. 2022, OpenAI’s chatbot ChatGPT has taken the world by storm. The AI tool quickly became the fastest-growing consumer application in history and kickstarted the launch of rival chatbots from companies such as Google-parent Alphabet and Microsoft.

Both Musk and Altman have been making headlines. Musk, considered the world’s richest person, runs electrical vehicle maker Tesla, rocket and satellite maker SpaceX and bought X, formerly Twitter, for $44 billion in Oct., 2022. He recently reported the advances of the brain chip technology implants produced by his startup Neuralink.

Altman has meanwhile had a rocky relationship with OpenAI. He was suddenly fired from the company in November last year, in a move that sent shockwaves across the tech industry. The American entrepreneur — one of the leading figures in the AI boom — returned to the firm a few days later.