Musk attorney Marc Toberoff said he submitted the bid to OpenAI's board of directors, according to the Journal.

"No thank you, but we will buy twitter for $9.74 billion if you want," OpenAI chief Sam Altman wrote in a post on X, formerly Twitter, apparently responding to the offer.

Musk, who bought X under its former moniker for $44 billion in 2022, replied to the post by simply writing: "Swindler."

The Tesla boss and close ally of US President Donald Trump has been mired in an ongoing feud with Altman, with Musk filing repeated lawsuits against the San Francisco-based company.

Musk co-founded OpenAI in 2015, which has become the world's leading AI startup since he left in 2018. He launched his own generative AI startup, xAI, in 2023.