WASHINGTON — US Senator Elizabeth Warren has asked Donald Trump’s transition team to hold Elon Musk to the same ethics standards as other transition members, putting oversight of the unusually powerful presidential adviser in the spotlight.

The billionaire CEO of Tesla and rocket company SpaceX, as well as the owner of social media platform X, has had an increasingly close relationship with Republican Trump since he endorsed him in July. Musk spent over a quarter billion dollars to help elect Trump, and also owns interests in cryptocurrency and other ventures.

“Mr. Musk’s substantial private interests present a massive conflict of interest with the role he has taken on as your ‘unofficial co-president,'” Warren said in a letter to the Trump transition team made public by her office on Tuesday (Dec 17).

“Currently, the American public has no way of knowing whether the advice that he is whispering to you in secret is good for the country — or merely good for his own bottom line.”