The legal showdown will center on Musk's claim that OpenAI and Altman abandoned the startup's original nonprofit, public-benefit mission and misled him while turning the lab into a highly lucrative, Microsoft-linked for-profit enterprise.

Musk alleges that Altman "intentionally courted and deceived" him by proposing a nonprofit that would serve as a counterweight to Google's DeepMind AI research unit and make AI technology open source for the benefit of humanity.

The suit claims OpenAI's leaders have since restructured the organization, created for-profit affiliates, and struck multibillion-dollar deals in a way that violated that mission.

The Tesla and SpaceX boss was an original co-founder of OpenAI and its biggest funder when it began in 2015, providing tens of millions of dollars in seed capital. He left three years later.

OpenAI went on to release ChatGPT in 2022 and Musk eventually launched a rival, xAI.

Microsoft, a major investor in OpenAI since 2019, has poured billions into the firm and become its biggest shareholder after a restructuring last year.

The trial, to be held before a jury, will be presided over by US District Judge Yvonne Gonzalez Rogers in Oakland, California.