Donald Trump announced on Thursday that if elected president he would appoint billionaire Elon Musk to lead an audit of government spending and implement "drastic" reform.

Trump said that at Musk's suggestion, he would "create a government efficiency commission tasked with conducting a complete financial and performance audit of the entire federal government," with the Tesla CEO as its chief.

Trump, who is known for hyperbole, told the Economic Club of New York the effort could save "trillions and trillions of dollars."

"This commission will develop an action plan to totally eliminate fraud and improper payments within six months," Trump said.

Musk – who has said he previously voted for Democratic candidates – has thrown his weight and considerable wealth behind Trump since a gunman tried to assassinate the former president at a rally in July.

Musk has a history of sparring with regulators, as when the Securities and Exchange Commission required vetting of his Twitter posts following 2018 tweets that the agency characterised as "false and misleading."

Other Musk initiatives, such as his pursuit of autonomous driving technology, also face oversight by government agencies. (AFP)