AVA- Krahenbuhl's remarks came during a meeting of Arab foreign ministers held at the Arab League headquarters in Cairo to discuss the repercussions of Washington's decision on the conditions of some 5.3 million Palestinian refugees.
The UNRWA chief hailed the donations of Saudi Arabia, the United Arab Emirates, Qatar and Kuwait to the UN agency.
"I humbly appeal to all of you to ensure that the pledges that were made are indeed transferred. Please do also consider opportunities for further donations at this critical time," he said.
Krahenbuhl pointed out that the support of oil-rich Gulf states and other donors enabled his agency to open the school year on time for 526,000 Palestinian students.
"This was the best possible response to give to the challenges we faced," he said, adding that UNRWA still needs 186 million U.S. dollars to ensure that the schools and clinics stay open and emergency services remain operational.
He also expressed his "deep regret and disappointment" at the decision to cut funding by the U.S., which used to be UNRWA's "historically most generous and consistent donor."
The Palestinian-Zionist conflict has been going on for decades, since the Zionist occupation of Palestinian territories and the Western-backed creation of Israel in 1948.
The U.S. has taken several measures to support to Zionist regime, including recognizing Jerusalem as Tel Aviv's capital last December and relocating the U.S. embassy in Israel from Tel Aviv to the disputed holy city later in May.
The Palestinians seek to establish an independent state with East Jerusalem as its capital in light of the UN-proposed two-state solution based on the pre-1967 borders.