WASHINGTON — The Trump administration’s decision to end American funding to a United Nations agency that provides assistance to millions of Palestinian refugees was denounced broadly on Friday by international officials, former United States diplomats and Palestinians who were reeling from the elimination of a decades-long policy of support.
The State Department announced the funding cut on Friday afternoon, after it had already been confirmed by a former senior official at the United States Agency for International Development who had spoken to journalists.
“The United States will no longer commit further funding to this irredeemably flawed operation,” Heather Nauert, the chief State Department spokeswoman, said in a written statement.
The move was pushed by Jared Kushner, President Trump’s son-in-law and top adviser on the Middle East, as part of a plan to compel Palestinian politicians to drop demands for most of the refugees to return to what they call their homeland.
At a meeting this month, Secretary of State Mike Pompeo argued against the drastic funding cut. But Mr. Kushner prevailed, said R. David Harden, who was briefed on the plans and oversaw projects in the Palestinian territories for more than a decade until leaving U.S.A.I.D. in April.
“What we’re seeing right now is a capricious move that has a very high risk of unsettling the region,” Mr. Harden said, noting that the relief agency supported about five million refugees.
Hanan Ashrawi, a member of the executive committee of the Palestine Liberation Organization, said the cuts could destabilize refugee camps not only in the West Bank and Gaza, but also in Jordan and Lebanon.
“If you deprive people of their education, their health — their future — this is extremely serious and dangerous,” she said. “Who is going to step in? If you want to hand them over to the religious schools, to Hamas, then you have to live with the consequences.”
Israeli officials did not comment on the cuts, although they have repeatedly expressed the view that the United Nations Relief and Works Agency, known as Unrwa, is a problem.
Israel’s government has accused the agency of continually expanding the population of refugees — and perpetuating the Israeli-Palestinian conflict — because it grants refugee status to the descendants of those displaced in the 1948 war that led to the creation of the state of Israel.
Each year, the State Department transfers money by the end of September to the United Nations agency.
In January, the State Department released $65 million for the agency and announced it was withholding another $60 million that had already been allocated in a budget process for 2018. The decision withdraws that amount and withholds any further money.
Since 2009, the annual contribution from the United States to the United Nations agency has ranged between $233 million and nearly $400 million — about a quarter of the agency’s budget. The United States is by far the biggest donor; other large donors include European and Middle Eastern nations.
R. Nicholas Burns, a Harvard Kennedy School professor and a former senior United States diplomat who has worked on the Palestinian issue, called the change “heartless and unwise” and a reflection of “the most one-sided U.S. policy since 1948,” when Harry S. Truman recognized the newly established state of Israel.
“The Trump Administration’s decision to end U.S. assistance to Palestinian refugees is wrong on every level,” Mr. Burns said on Twitter on Friday. “It will harm innocent people, particularly young Palestinians.”
The Trump administration has been working to change several decades-old pillars of United States policy on Israel. Last December, Mr. Trump announced that he was recognizing Jerusalem as the capital of Israel.
Mr. Kushner has been working on a peace proposal in the Israeli-Palestinian conflict and is pushing Palestinian leaders to drop demands for the right of most of the five million refugees to return to Israeli-controlled land.
The vast majority of the five million refugees are descendants of Palestinians displaced in the mid-20th century. The United Nations aid agency officially considers all of them refugees, consistent with international law and United Nations refugee protocols, said Peter Mulrean, director of the Unrwa office at the United Nations.
Mr. Kushner and other American officials are seeking to change the United Nations designation in hopes the agency will alter the debate over which Palestinians have the right of return.
Mr. Harden said those American officials also believe that defunding the aid agency will give them leverage to force Palestinian and other Arab leaders to drop — or at least lessen — the demand for right of return, which is one of the greatest points of contention between Israeli and Palestinian officials.
By attempting to redefine the Palestinian refugee problem, Ms. Ashrawi said, Washington was once again coming down squarely on Israel’s side. And that, she said, could only weaken moderates and reignite conflict.
“We are back to all or nothing, to confrontations,” Ms. Ashrawi said. “We have done so much to show good will, and now we are being told, no, Israel has to have it all.”
The Trump administration announced last week that it was diverting $200 million set aside for Palestinian aid in the West Bank and Gaza. That money had been appropriated by Congress in the 2017 budget to the Agency for International Development, and is part of a package of assistance given annually to help the Palestinians that is separate from the United Nations allocation.
About $35 million of this assistance could still go forward, Mr. Harden said, as well as tens of millions of dollars from the State Department for Palestinian security forces.
Chris Gunness, a spokesman for the United Nations agency, said: “We reject in the strongest possible terms the criticism that Unrwa’s schools, health centers, and emergency assistance programs are ‘irredeemably flawed.’ These very programs have a proven track record in creating one of the most successful human development processes and results in the Middle East.”
Elizabeth Campbell, a spokeswoman for the agency, said that “Unrwa is a public good, providing critical services, such as vaccinations and prenatal care, that are otherwise unavailable to refugees.”
Asked on Tuesday about potential funding cuts, Nikki R. Haley, the United States ambassador to the United Nations, did not directly confirm the decision to eliminate the Unrwa aid, which was first reported by Foreign Policy magazine.
“First of all, you’re looking at the fact that there’s an endless number of refugees that continue to get assistance,” Ms. Haley said during a security conference in Washington. “But more importantly, the Palestinians continue to bash America.”
Israel’s defense establishment has long warned that sudden cuts to the agency’s funding could prove destabilizing, if not explosive.
In Gaza, roughly half the population depends on Unrwa aid. In the West Bank, where the refugee population is smaller, refugee camps are already the source of much violence, both against other Palestinians and against Israelis.
“Hamas is constantly trying to conduct attacks from the West Bank,” said Peter Lerner, a retired Israeli military spokesman who has argued against cuts. “Why give them more incentive? Instead of kids going to school or to vocational-training centers, they’ll have no place to be.”
In Jordan, where more than two million Palestinian refugees live, the foreign minister, Ayman Safadi, has said the nation would intensify efforts to bridge any agency funding deficit and to rally support for the agency.
“It is an extremely difficult situation,” he said in a BBC interview that aired on Friday, “the consequences of which will be devastating to communities.”
David M. Halbfinger contributed reporting from Jerusalem, Rana Sweis from Amman, Gardiner Harris from Washington and Rick Gladstone from New York.