The United Nations Relief and Works Agency for Palestine Refugees (UNRWA) is facing an “existential” budget crisis and appealing for urgent funding to keep its essential functions running, the agency’s chief said Friday.

UNRWA Commissioner-General Philippe Lazzarini told reporters at the UN headquarters in New York that the organization needed "predictability" for its operations.

UNRWA said it will seek a new injection of funds at an upcoming donor conference, after it withstood years of financial instability during the administration of former United States President Donald Trump.

To fund UNRWA's "three core activities" -- education, health and social services -- "we are seeking $800 million a year," he told reporters ahead of the gathering, organized by Jordan and Sweden.

"The main objective of the conference is to have a better predictability" and to "promote visibility" the Swiss diplomat said.

"Today we keep struggling, running after cash," he said. "I never know as a Commissioner-General weeks ahead if I would be able to pay the salaries of 28,000 staff."

UNRWA provides assistance to more than five million Palestinians registered with it in the Palestinian territories, Lebanon and Jordan.

Washington had stopped nearly all aid to UNRWA in 2018 under Trump, who rejected the very idea of Palestinians being refugees.

The US had been the single largest donor to the agency, contributing about 30 percent (nearly $365m) of UNRWA’s annual budget.