Commissioner General Pierre Krähenbühl of the UN Relief and Works Agency also said it has received no specifics about reforms sought by the United States, suggesting politics—notably surrounding the US decision to recognize Jerusalem as the Israeli capital—were at play.
UNRWA, which serves some 5 million Palestinian refugees and their descendants, had a budget of over $1 billion last year. This covered long-running programs, including education, as well as emergency funds for crises such as the war in Syria.
The US has been the largest donor, giving one-third of the total budget. The Trump administration withheld half of the first installment of payments this year, demanding reforms as a condition for future aid.
The Trump administration has committed $60 million this year—far short of the $360 million that the US provided last year—and Krähenbühl said he has no sign that other US funding might be on the way.
"Evidently, that is a very severe and dramatic change in the parameters of funding from the United States," which he called a "stable, predictable and most-generous contributor to UNRWA over decades."
"It is clear that we have a very big task on our hand to fill that gap," Krähenbühl told reporters in Geneva.
UNRWA responded by calling on donors to speed up their funding, and Switzerland, Finland, Denmark, Sweden, Norway, Germany, Russia, Belgium, Kuwait, the Netherlands and Ireland have taken steps to do so, he said. Others were considering similar action.
"Advancing contributions is extremely important to help us address the first few months," he said. "Of course, a shortfall of 300 million can only be addressed with obtaining additional income from other sources over the year."
The comments Tuesday came as UNRWA said it is seeking $800 million for emergency operations in Syria, the West Bank and Gaza Strip this year. UNRWA sought $400 million each for Syria and the Palestinian territories. In an appeal last week, the agency sought an additional $500 million.
"We signed our new framework agreement with the US in the beginning of December in which every aspect of our relationship from funding to reform discussions was covered and agreed," Krähenbühl said. "They did not explain the current decision by reform-related elements."
He said he believed the funding cut was linked to the Trump administration's decision to recognize Jerusalem as Israel's capital and a subsequent vote by the UN General Assembly to denounce the decision.
"It is very clear that the decision by the United States was not related to our performance," he said. "This has to be part of the debate that took place around Jerusalem."