Washington DC - Elon Musk outlined plans Wednesday for his new role as "efficiency" czar – signaling an assault on federal spending and staffing that would be backed by President-elect Donald Trump's executive powers and a conservative Supreme Court.

Writing in the Wall Street Journal, the world's richest man said he was taking aim at hundreds of billions of dollars in government spending – including funding for public broadcasting and international aid – as well as at bureaucracy that represents, according to him, an "existential threat" to US democracy.

The Tesla and SpaceX CEO, who also owns the X social media platform, said that he and Vivek Ramaswamy, a fellow businessman and Trump loyalist, would work to slash federal regulations and make major administrative changes.

"We are entrepreneurs, not politicians. We will serve as outside volunteers, not federal officials or employees," Musk and Ramaswamy wrote in their most detailed remarks since Trump named them heads of a new so-called Department of Government Efficiency.

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They said DOGE – expected to function more as an advisory group rather than a formal department – will prepare a list of regulations which Trump could invalidate unilaterally.

"When the president nullifies thousands of such regulations, critics will allege executive overreach. In fact, it will be correcting the executive overreach of thousands of regulations promulgated by administrative fiat that were never authorized by Congress," they said.

Musk and Ramaswamy added that a reduction in regulations would pave the way for "mass head-count reductions across the federal bureaucracy" and said DOGE would aim to cut more than $500 billion in government expenditures.

Moves to gut programs will almost certainly face political pushback, even from Republicans, and prompt legal challenges.

However, Musk and Ramaswamy voiced confidence that recent rulings by the conservative-dominated Supreme Court would allow them to push through the ambitious agenda.

"With a decisive electoral mandate and a 6-3 conservative majority on the Supreme Court, DOGE has a historic opportunity for structural reductions in the federal government," they said.

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They said that DOGE's top goal was to not be needed by July 4, 2026, which was described as an expiration date for the project.

Musk became a close ally to Trump during his campaign, reportedly spending over $100 million to boost his presidential bid and joining him at rallies.

However, with Musk's businesses all having varying degrees of interactions with US and foreign governments, his new position also raises concerns about conflict of interest.

The South African-born billionaire invited Trump to watch a test flight of his SpaceX company on Tuesday in a sign of ever closer ties between the pair.

But their relationship – defined by combustible personalities and some past policy differences – could be subject to friction once the reality of political life sets in.