The World Health Organisation has begun a process of fixing new priorities and announced a one-year limit on staff contracts, an internal memo shows, as it aims to make the UN agency more sustainable after the US withdrawal.

The memo, dated March 10 and signed by WHO's assistant director-general Raul Thomas, laid out further cost-cutting measures - the latest in a series of such steps since US President Donald Trump's announcement in January.

Senior WHO officials have begun "prioritisation" work in the past three weeks to make the global health agency sustainable, the document says.

"While operating in an extremely fluid environment, WHO's senior management are working to navigate these shifting tides by undertaking a prioritisation process," the memo said.

"Their work will ensure that every resource is directed toward the most pressing priorities while preserving WHO's ability to make a lasting impact."

It said staff were working to secure additional funding from countries, private donors and philanthropists, without saying if these processes had been successful.

It stopped short of announcing immediate staff cuts but said that "given the magnitude of the challenges we face, some difficult decisions are unavoidable".

A WHO spokesperson did not immediately respond to a request for comment.