The United Nations has launched an urgent financial appeal for its emergency programmes in Syria and the occupied Palestinian territories.
UN's Relief and Works Agency (UNRWA) said on Tuesday it needs $800m to provide life-saving aid including food, water, shelter and medical assistance.
Pierre Krahenbuhl, UNRWA's commissioner-general, said the funds were needed to enable the agency to "continue delivering desperately needed relief to those affected by deepening emergency situations".
"However, the agency's critical financial crisis following the reduction in the US funds threatens our ability to deliver these vital services," he said.
The United States said this month that it was withholding half of the $125m it had planned to give to the agency.
UNRWA received $360m from the US in 2017, but this year, Washington has only cleared $60m.
Meanwhile, more than 10 countries have said they will advance their donations to finance the agency, which runs schools and clinics for more than five million Palestinians across the Middle East, in the coming weeks.
Denmark, Finland, Germany, Norway, Russia, Sweden and Switzerland have already have transferred early funds while Belgium, Ireland, Kuwait and the Netherlands have pledged to do so soon, Krahenbuhl said.
Jerusalem's status is an extremely sensitive aspect of the Israeli-Palestinian conflict.
Israel claims the city as its capital, following the occupation of East Jerusalem in the 1967 War, and considers Jerusalem to be a "united" city. The western half of the city had been captured in the 1948 Arab-Israeli War.
Israel's occupation of East Jerusalem effectively put the entire city under de facto Israeli control. Israeli jurisdiction and ownership of Jerusalem, however, is not recognised by the international community, including the US.
Palestinians have long seen East Jerusalem as the capital of their future state. They say that a US move to relocate the embassy would prejudge one of the most sensitive issues in the conflict - the status of Jerusalem - and undermine Washington's status as an honest mediator.
No country currently has its embassy in Jerusalem.