Elon Musk has begun swinging his wrecking ball at the US government, with concerns growing over the unprecedented power that President Donald Trump has handed to the world's richest man.

The South African born billionaire has taken control over the US Treasury's payments system that manages trillions of dollars. He single-handedly announced the demise of the USAID humanitarian agency. He has helped drive out top officials.

For a man who likes to rail against unelected bureaucrats, the unelected Space X and Tesla tycoon has been subject to little accountability as he pushes Trump's drive to shrink the US government.

Trump sought to play down the issue Monday when asked about it in the Oval Office, saying "Elon can't do and won't do anything without our approval."

"We'll give him the approval where appropriate, where not appropriate we won't. But he reports in," insisted Trump. "It's something that he feels very strongly about and I'm impressed."

Musk's powers have seemed almost unbounded, leading to accusations by Democrats of an unconstitutional power grab by both him and his fellow business mogul Trump.

So far Musk has been registered as neither a federal employee nor a government official -- although US media reported Monday that he had now been registered as a "special government employee."

Critics point to the fact that Musk was the biggest donor to Trump's victorious election campaign, to the tune of a quarter of a billion dollars.

Then there is the fact that his companies also have huge US government contracts.

'DOGE kids'

And while a cute cartoon dog initially adorned the website of Musk's "Department of Government Efficiency" (DOGE), its later replacement by a dollar sign in a gold circle underscored what the focus would be.

His young team of so-called "Doge Kids," drawn from his own companies, dramatically seized control of the US Treasury Department's payments system and took key government positions.

They have helped push a drive to get federal employees to take severance payments and quit, with an email that closely resembles a message sent to Twitter employees when Musk took over and later renamed the social network X.

Musk personally announced that the massive USAID humanitarian agency would be "shutting down" -- during a live chat on X -- and branded it a "criminal organization."

Their no-holds barred style has raised eyebrows.

A dramatic stand-off reportedly ensued when Musk's aides demanded access to a secure room at USAID where classified information was held.

There was a similar situation when a career Treasury official was reportedly put on administrative leave after refusing such access to aides.

And the head of the Federal Aviation Administration stepped down on Inauguration Day after Musk had criticized the agency's oversight of rocket launches. Days later Trump had to rush to appoint a new head after a deadly passenger jet crash in Washington.

A controversy over a raised-arm salute by Musk on the day of Trump's inauguration only added to the controversy.

'Tiger in the petting zoo'

Trump insisted Monday that "if there's a conflict we won't let him get near it" -- but that did not calm critics.

Democrats, who have been largely silent during Trump's first shock-and-awe two weeks in power, began to mobilize against the latest Musk moves.

"No one elected Elon Musk," Senator Elizabeth Warren said.

Democrats on the US House Ways and Means Committee were holding an emergency call partly devoted to the issue.

They have bitterly criticized DOGE as an unconstitutional attempt to exert presidential power over funds approved by Congress.

"It's like letting a tiger into the petting zoo and hoping for the best," Democratic Senate Minority Leader Chuck Schumer said Monday.

Speaking at a protest by USAID workers, Senator Chris Van Hollen said "this Elon Musk attempted takeover... will not stand."

Washington is however closely watching to see if the egos of two consummate showmen like Trump and Musk can survive in the same White House for long.

Indeed Musk is reportedly not in the same building, after being denied a West Wing office for his staff, and getting premises instead in the Eisenhower Building, a separate part of the White House complex.