WASHINGTON, United States (AFP) — Elon Musk, the world’s richest person and United States (US) President Donald Trump’s controversial close advisor, said Monday the giant US Agency for International Development (USAID) humanitarian agency will be “shutting down” as part of his radical — and critics say unconstitutional — drive to shrink the US government.

Employees at USAID, which runs aid programmes 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 called USAID “a criminal organisation” and declared “you’ve got 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 Trump’s presidential campaign — said he had cleared the unprecedented move against a major wing of US government with Trump himself.

“I went over with him in detail, and he agreed that we should shut it down,” Musk said in a discussion on his X online platform.

USAID is the aid arm of US foreign policy, funding health and emergency programmes in the world’s poorest regions. It is also seen as an important source of soft power for the superpower in its struggle for influence with rivals including China.

Echoing far-right Republicans, Musk used X to call the agency “a viper’s nest of radical-left marxists who hate America”.

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

Congress has authority over the US budget but Musk — 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 a federal employee nor a 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 on swaths of Americans.

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

“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.