A consortium of investors led by Musk offered $97.4 billion to buy the assets of OpenAI's nonprofit, in another salvo from the world's richest man against the artificial intelligence startup.Musk sued OpenAI CEO Sam Altman and others in August and has asked a US district judge to block OpenAI's attempt to transition to a for-profit entity.OpenAI in its letter, submitted to a federal court on Wednesday, said Musk had contradicted himself when making "an improper bid to undermine a competitor."Musk's court filings assert that OpenAI's assets must remain within a charitable trust and should not be transferred for private gain.That contrasts with his proposed acquisition which seeks to transfer all OpenAI assets to him and his private investors, OpenAI said.Representatives for Musk did not respond to an emailed request for comment.Musk co-founded OpenAI with Altman in 2015 as a nonprofit but left before ChatGPT went viral at the end of 2022. He founded the competing AI startup xAI in 2023.OpenAI has said it wants to become a for-profit organisation to secure the capital needed to develop the best AI models.