Washington DC - Billionaire Elon Musk on Wednesday announced he was leaving his role in US government 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 DOGE mission will only strengthen over time as it becomes a way of life throughout the government," he added.

The South African-born 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.

Britney Spears Britney Spears makes major business move after concerning plane incident

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, an excerpt of which aired late Tuesday.

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

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, which will be aired in full on Sunday.

Elon Musk Musk trashes Trump's "Big Beautiful Bill" as rift with administration widens

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 X after the tech titan's comments aired.

All DOGE cuts would have to be carried out through a separate bill targeting the federal bureaucracy, according to US Senate rules, Miller added.

But 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.

Musk complained in a separate interview with the Washington Post that DOGE, which operated out of the White House with a staff of young technicians, had become a lightning rod for criticism.

"DOGE is just becoming the whipping boy for everything," Musk told the newspaper at the Starbase launch site in Texas ahead of Space X's latest launch on Tuesday.

"Something bad would happen anywhere, and we would get blamed for it even if we had nothing to do with it."

Musk blamed entrenched US bureaucracy for DOGE's failure to achieve all of its goals – although reports say his domineering style and lack of familiarity with the currents of Washington politics were also major factors.

"The federal bureaucracy situation is much worse than I realized," he said. "I thought there were problems, but it sure is an uphill battle trying to improve things in DC, to say the least."

Musk has previously admitted that he did not achieve all his goals with DOGE even though tens of thousands of people were removed from government payrolls and several departments were gutted or shut down.

Musk's own businesses suffered in the meantime.

Protesters against the cost-cutting targeted Tesla dealerships while arsonists even torched a few of the electric vehicles, and the firm's profits slumped.

"People were burning Teslas. Why would you do that? That’s really uncool," Musk told the Post.

"Musk’s exit is an enormous victory for Democrats and working people," Democratic Congressman Greg Casar said in a statement. "This is a sign of how powerful the anti-corruption, anti-billionaire movement in American politics can be. Musk did not choose to leave because Elon Musk likes to follow the rules. Musk will leave because the American people built enough political pressure that he had no choice."

Musk has been focusing on Space X after a series of fiery setbacks to his dreams of colonizing Mars – the latest of which came on Tuesday when its prototype Starship exploded over the Indian Ocean.

"Musk’s exit is an enormous victory for Democrats and working people. This is a sign of how powerful the anti-corruption, anti-billionaire movement in American politics can be. Musk did not choose to leave because Elon Musk likes to follow the rules. Musk will leave because the American people built enough political pressure that he had no choice."

The tycoon last week also said he would pull back from spending his fortune on politics, having spent around a quarter of a billion dollars to support Trump.