By Anna Tong

OAKLAND, April 4 (Reuters) - - Billionaire Elon Musk's lawsuit against OpenAI will go to a jury trial in spring 2026, the federal judge presiding over the case decided on Friday.

Last month, OpenAI and Musk agreed to fast-track a trial over OpenAI's for-profit shift, the latest turn in a grudge match between the world's richest person and OpenAI CEO Sam Altman playing out publicly in court.

The judge, Yvonne Gonzalez Rogers of the U.S. District Court for the Northern District of California, had denied Musk's request to pause the ChatGPT maker's transition to a for-profit model and instead proposed an expedited trial.

Musk cofounded OpenAI with Altman in 2015 but left before the company took off and subsequently founded the competing startup xAI in 2023. xAI last month acquired Musk's social media company X in a deal that values X at $33 billion and allows the value of his artificial intelligence firm to be shared with co-investors in X.

Last year, Musk, who is also the CEO of Tesla TSLA.O, sued OpenAI and Altman, accusing OpenAI of straying from its founding mission — to develop AI for the good of humanity, not corporate profit.

OpenAI and Altman have denied the allegations, while Altman alleges that Musk has been trying to slow down a competitor.

At stake in the lawsuit is the ChatGPT maker's transition to a for-profit model, which the startup says is crucial to raising more capital and competing well in the expensive AI race.

OpenAI is under pressure to transition quickly. The company is currently raising a funding round of up to $40 billion led by Japanese tech investment group SoftBank. SoftBank said it has agreed to fund OpenAI with $10 billion in mid-April and an additional $30 billion in December, contingent on the firm's transitioning to a for-profit by the end of the year.

Altman, who has said OpenAI is not for sale, rejected a $97.4 billion unsolicited takeover bid earlier this year from a Musk-led consortium with a "no thank you."

(Reporting by Anna Tong in Oakland, California; Editing by Leslie Adler)

((anna.tong@thomsonreuters.com; Mob: +1-650-468-3913))