The leaked notice follows President Trump’s executive order issued on Monday for a 90-day pause in foreign development assistance pending a review of efficiencies and consistency with his foreign policy.

The United States is the world’s biggest international aid donor spending $68bn in 2023 according to government figures. The State Department notice appears to affect everything from development assistance to military aid.

It makes exceptions only for emergency food aid and for military funding for Israel and Egypt. The leaked memo’s contents have been confirmed by the BBC.

“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… it’s extremely broad,” 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.

The AFP news agency reported the funding freeze could also potentially affect Ukraine, which received billions of dollars in weapons under Trump’s predecessor Joe Biden.

Rubio’s memo, justifying the freeze, said it was impossible for the new administration to assess whether existing foreign aid commitments “are not duplicated, are effective and are consistent with President Trump’s foreign policy”.

Rubio has issued a waiver for emergency food assistance, according to the memo.

This comes amid a surge of humanitarian aid into the Gaza Strip after a ceasefire between Israel and Hamas began, and several other hunger crises around the world, including Sudan.

The memo also said waivers have so far been approved by Rubio for “foreign military financing for Israel and Egypt and administrative expenses, including salaries, necessary to administer foreign military financing”.

The State Department has been approached for comment.