Elon Musk denied leading a "hostile takeover" of the US government and defended his cost-cutting plans as he made a surprise first appearance at the White House on Tuesday.

The world's richest man took questions from reporters in the Oval Office as he stood next to President Donald Trump, who has tasked him with slashing the size and spending of the federal government.

Trump then signed an order giving Musk's Department of Government Efficiency (Doge) more authority to cut the federal workforce. It instructed the heads of government agencies to comply with Doge.

The agency has been criticised by Democrats who have accused it of a lack of transparency, and its efforts have also been hampered by legal challenges.

But Musk, who was questioned by reporters for the first time since Trump took office last month, described sweeping government cuts as "common sense" measures that are "not draconian or radical".

"The people voted for major government reform and that's what the people are going to get," he said. "That's what democracy is all about."

"I fully expect to be scrutinised," he added. "It's not like I think I can get away with something."

The billionaire technology entrepreneur, who himself was appointed and not elected, described federal workers as an "unelected, fourth, unconstitutional branch of government" that he said has "more power than any elected representative".

The 53-year-old owner of Tesla, X and SpaceX wore a black Make America Great Again cap and cracked the occasional joke with reporters who asked him about his critics. He had his young son, named X Æ A-Xii - or X for short - on his shoulders for part of the news conference.

"It's not optional for us to reduce the federal expenses," Musk said. "It's essential. It's essential for America to remain solvent as a country."

Musk was also asked about a recent false claim that the US government was sending millions of dollars worth of condoms to Gaza. "Some of the things that I say will be incorrect and should be corrected," Musk replied.

In the first weeks of Trump's term, Musk has spearheaded the effort to rapidly shrink the federal government. Doge representatives have entered various departments to monitor spending, offered millions of workers an exit route and moved to freeze federal funding as well as the work of agencies such as the US Agency for International Development (USAID).

"We found fraud and abuse," Trump said of Musk's work on Tuesday, without providing evidence. He estimated more than $1 trillion in wasteful spending would be discovered although gave no further details.

The vast cost-cutting drive has been criticised repeatedly by opponents including senior Democrats and those who say it will have significant repercussions both in the US and internationally.

"An unelected shadow government is conducting a hostile takeover of the federal government," Senate Minority Leader Chuck Schumer said recently. He said Democrats would work to block Musk's efforts by introducing specific language into spending bills.

But with Republicans holding a majority in both chambers of Congress, Trump's agenda has faced more pressing hurdles in the courtroom.

"I hope that the court system is going to allow us to do what we have to do," Trump said on Tuesday, referring to recent judgments that have temporarily halted his efforts to shrink government, including through an employee buyout programme.

Critics of Doge have also pointed to potential conflicts of interest given Musk's many business interests. Democrats have accused him of personally benefiting from some of the changes the Trump administration is trying to push through.

Musk said the public could take its own view about potential conflicts. Trump then said if the White House thought there was a lack of transparency or a conflict of interest, "we would not let him do that segment or look in that area".

Trump then signed an executive order instructing Doge to "significantly" cut down the size of the federal workforce. The order also calls on government offices to "undertake plans for large-scale reductions in force".

It also says that once a hiring freeze that Trump signed on his first day ends, that agencies should hire no more than one person for every four who depart.

A recent poll by the BBC's US partner CBS News indicated a majority of Americans are in favour of Musk's work, but disagree over how much influence he should have.

It suggested Republicans in particular supported his efforts to cut federal spending and foreign aid.

The poll indicated largely favourable ratings for Trump's policies, however, some 66% of people said they wanted him to focus more on lowering prices.

One of the agencies that has been most affected by the cost-cutting drive is USAID.

On Tuesday, the inspector general of the agency was fired - one day after releasing a report criticising plans to put the vast majority of the agency's staff on leave and close US-backed aid programmes around the world.