The White House on Thursday vowed that its massive federal government slashing drive would continue, even after the departure of cost-cutter-in-chief Elon Musk, who the administration thanked for his service.

US President Donald Trump had tasked Musk with cutting government spending as head of the so-called Department of Government Efficiency (DOGE) but, after a feverish start, the billionaire recently announced he was stepping back to focus on his companies, including Tesla and SpaceX.

"We thank him for his service. We thank him for getting DOGE off of the ground, and the efforts to cut waste, fraud and abuse will continue," White House Press Secretary Karoline Leavitt told reporters.

Musk has paid tribute to Trump, but also criticised the US president's signature spending bill, saying it would increase the national deficit and undermine the cost-cutting work.

Trump's "One Big, Beautiful Bill Act" – which passed the US House last week and now moves to the Senate – offers sprawling tax relief and spending cuts and is the centrepiece of his domestic agenda.

But Musk, a key Trump advisor and financial backer, said in a CBS interview that he was "disappointed to see the massive spending bill, frankly".

The world's richest person last week also said he would pull back from spending on politics, having contributed around a quarter of a billion dollars to support Trump's election campaign. (AFP)