OpenAI CEO Sam Altman said he doesn’t admire his onetime collaborator, Elon Musk, as much as he once did.

Altman said in an interview with former Fox News anchor Tucker Carlson, which aired on YouTube on Wednesday, when he was asked about his views on Musk. The pair cofounded OpenAI in 2015, but their relationship broke down after Musk left its board in 2018.

“For a long time, I looked up to him as an incredible hero, a great jewel for humanity. I have different feelings now,” Altman said of Musk.

“There are things about him that are incredible, and I’m grateful for a lot of things he’s done. There’s a lot of things about him that I think are traits I don’t admire,” he added.

Representatives for Altman and Musk did not respond to requests for comment from Business Insider.

Musk was one of OpenAI’s financial backers during the early days of its founding, though it is unclear how much money he contributed to the ChatGPT maker.

In March 2023, Musk said he gave about $100 million to the company. OpenAI, however, said in March 2024 that Musk’s contributions were less than $45 million.

Since leaving OpenAI’s board, Musk has publicly criticized Altman’s leadership.

In February 2024, Musk sued Altman and OpenAI, accusing them of violating its nonprofit mission when it partnered with Microsoft. He withdrew the lawsuit in June 2024 but refiled it in August 2024.

“Change your name to ClosedAI and I will drop the lawsuit,” Musk wrote in an X post in March 2024.

Last month, Musk threatened to sue Apple over what he said was the iPhone maker’s bias toward OpenAI on its App Store. Musk said Apple had committed an “unequivocal antitrust violation” and filed a lawsuit against Apple and OpenAI on August 25.

“This is a remarkable claim given what I have heard alleged that Elon does to manipulate X to benefit himself and his own companies and harm his competitors and people he doesn’t like,” Altman wrote in an X post last month in response to Musk.

Musk has also been busy building his own competitor to OpenAI. In July 2023, he launched his own AI startup, xAI.

xAI raised over $12 billion during funding rounds last year and was valued at a reported $50 billion. In June, Morgan Stanley said xAI raised $10 billion in debt and equity to develop its data centers and chatbot, Grok. OpenAI’s last funding round valued it at a reported $300 billion.

Altman said Musk had told him he was leaving OpenAI because he didn’t think it was on a “trajectory to be successful.”

“Then, we did OK. I think he got understandably upset. I would feel bad in that situation,” Altman told Carlson.