“No new funds shall be obligated for new awards or extensions of existing awards until each proposed new award or extension has been reviewed and approved,” says the memo to staff.

It adds that US officials “shall immediately issue stop-work orders, consistent with the terms of the relevant award, until such time as the secretary shall determine, following a review.”

It also orders a wide scale review of all foreign assistance to be completed within 85 days to ensure the aid adheres to President Trump’s foreign policy goals.

Secretary of State Marco Rubio – the US’s top diplomat – has previously stated that all US spending abroad should take place only if it makes America “stronger”, “safer” or “more prosperous”.

One former senior State Department official told the BBC the notice meant a “potentially huge” impact on foreign aid programmes funded by the US.

“One can imagine, for example, the humanitarian de-mining programmes around the world suddenly being told stop work. That’s a pretty big deal,” said Josh Paul, who oversaw Congressional relations on weapons transfers at the State Department until late 2023.

Dave Harden, a former US Agency of International Aid (USAID) mission director in the Middle East, told the BBC the move was “very significant”, saying it could see humanitarian and development programmes funded by the US around the world being immediately suspended, while the review is carried out.

He said it could affect a wide range of critical development projects including water, sanitation and shelter.

“The employees of the implementing partner or the [non-governmental organisation] would be able to be paid, but actual assistance, I think, needs to be halted,” said Mr Harden.

“I have gone through [assistance suspensions] many times when I was the West Bank and Gaza mission director, but that was specific to that account. This is global,” he said.

“Not only does it pause assistance, but it puts a ‘stop work’ order in existing contracts that are already funded and underway. It’s extremely broad,” he added.