Musk has his own AI company called xAI which is behind the chatbot Grok.
CNBC has reached out to Toberoff, Tesla and X for comment.
'I'm not the one who tweeted funding secured'
Altman also dismissed a suggestion from Musk earlier this year that OpenAI lacks the money to contribute to President Donald Trump's multi-billion-dollar "Stargate" joint venture aimed at investing in U.S. computing infrastructure needed to train and run frontier AI models.