WASHINGTON -- Billionaire Elon Musk on Wednesday announced he was leaving his role in US government, intended to reduce federal spending, shortly after his first major break with President Donald Trump over his signature spending bill.

"As my scheduled time as a Special Government Employee comes to an end, I would like to thank President Donald Trump for the opportunity to reduce wasteful spending," he wrote on his social media platform X.

The tech tycoon had said Trump's bill would increase the deficit and undermine the work of Department of Government Efficiency (DOGE), which has fired tens of thousands of people.

Musk -- who was a constant presence at Trump's side before pulling back to focus on his Space X and Tesla businesses -- also complained that DOGE had become a "whipping boy" for dissatisfaction with the administration.

"I was disappointed to see the massive spending bill, frankly, which increases the budget deficit, not just decreases it, and undermines the work that the DOGE team is doing," Musk said in an interview with CBS News.

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 centerpiece of his domestic agenda.

But critics warn it will decimate health care and balloon the national deficit by as much as $4 trillion over a decade.

"A bill can be big, or it can be beautiful. But I don't know if it can be both. My personal opinion," Musk said in the interview.

The White House sought to play down any differences over US government spending, without directly naming Musk.

"The Big Beautiful Bill is NOT an annual budget bill," Trump's Deputy Chief of Staff Stephen Miller said on Musk's social network, X, after the tech titan's comments aired.

Musk's comments represented a rare split with the Republican president whom he helped propel back to power, as the largest donor to his 2024 election campaign.

Trump tasked Musk with cutting government spending as head of DOGE, but after a feverish start Musk announced in late April he was mostly stepping back to run his companies again.

AFP