The United States suspended USD 65 million to the United Nations Relief and Work Agency (UNRWA) earlier this month, as well as a separate USD 45 million in food aid.
Thousands of teachers, medical professionals and other staff gathered in Gaza City to protest the cuts that UNRWA officials have warned could threaten the education of more than half a million children.
The agency provides support for more than three million Palestinians across the Middle East.
Addressing the United States, he warned Trump of politicising humanitarian aid for millions of impoverished people.
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"You have been our biggest partner for decades, the United States, and you have helped us build one of the most effective and results-orientated public service organisations in the world.
"Protect this investment -- all these people that are doing something good in the lives of refugees."
Trump has accused the Palestinians of refusing to engage in peace talks with Israel, saying last week they would suspend funding of aid until they returned to the table.
The Palestinian leadership froze ties with the Trump administration after his controversial recognition of Jerusalem as Israel's capital, saying Washington could no longer be the main mediator in talks with Israel.
The Palestinians see east Jerusalem as the capital of their future state.