Washington DC - Elon Musk said Monday the USAID humanitarian agency will be "shutting down" as part of his radical and potentially unconstitutional drive to dismantle government institutions.

Employees at the US Agency for International Development, which runs aid programs in about 120 countries, were instructed by email not to go to their offices Monday. Some 600 staffers found themselves locked out of their computer systems, ABC News reported.

Musk previously called USAID "a criminal organization" and announced his intention "to basically get rid of the whole thing."

The founder of SpaceX and Tesla – who has massive contracts with the US government and was the biggest donor to President Donald Trump's campaign – said he had cleared the unprecedented move against a major wing of US government with Trump himself.

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"I went over with him in detail, and he agreed that we should shut it down," Musk said on X.

USAID is the aid arm of US foreign policy, funding health and emergency programs in the world's poorest regions. It is also seen as a weapon in the propaganda wars waged against US rivals.

The agency describes itself as working "to end extreme poverty and promote resilient, democratic societies while advancing our security and prosperity."

Its budget of more than $40 billion is a small drop in overall US government annual spending of nearly $7 trillion.

Echoing far-right Republicans, Musk has called USAID "a viper's next of radical-left marxists who hate America," falsely accusing it of funding "bioweapon research, including Covid-19, that killed millions of people."

Trump agreed Sunday, saying USAID is "run by a bunch of radical lunatics."

Democrats, who hold the minority in Congress, are sounding alarm over what they say is an unconstitutional power grab by Trump and Musk.

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Congress has authority over the US budget, but the far-right billionaire – whose so-called Department of Government Efficiency (DOGE) is not even a formal government agency – says he can decide how money is used.

Because Musk is neither elected, nor a federal employee or government official, it remains unclear to whom he or his informal agency are accountable – other than to Trump.

The pace and intensity of Musk's operation, which is using employees brought from his own companies, has caught opponents off guard.

In one especially tense episode, Musk's team insisted on gaining access to the Treasury's highly sensitive payment system, which is used for dispatching trillions of dollars a year across the entire government. It also contains the personal data of millions of Americans.

Unable to prevent this, the top civil servant at the Treasury Department, David Lebryk, reportedly left his job Friday.

"I can think of no good reason why political operators who have demonstrated a blatant disregard for the law would need access to these sensitive, mission-critical systems," Democratic Senator Ron Wyden wrote in a letter to Trump's new Treasury secretary, Scott Bessent.