The step will cost the United Nations Educational, Scientific and Cultural Organization one-quarter of its yearly budget the 22 percent contributed by the United States (about $70 million) plus another 3 percent contributed by Israel. Victoria Nuland, a State Department spokeswoman, said that American contributions to Unesco, including $60 million scheduled for this month, would not be paid.

Cheers filled the hall at Unesco’s headquarters here after the vote, with one delegate shouting, “Long live Palestine!” in French. The Palestinian foreign minister, Riad al-Malki, praised the organization, saying that “this vote will help erase a tiny part of the injustice done to the Palestinian people” and that it would help protect world heritage sites in Israeli-occupied territory.

In a long speech, Mr. Malki said that “this membership will be the best step toward peace and stability,” insisting that the Palestinian request for membership in Unesco was “linked in no way to our request to join the United Nations.”

The Obama administration, which values its membership in Unesco, tried unsuccessfully to keep the vote from taking place, while Irina Bokova, the American-supported director general of the organization, traveled to Washington to meet with Congressional leaders and ask them to alter the law.

Legislation dating from 1990 and 1994 mandates a complete cutoff of American financing to any United Nations agency that accepts the Palestinians as a full member. State Department lawyers see no leeway in the legislation, and no possibility of a waiver.

The American ambassador to the organization, David T. Killion, repeatedly called the vote on Monday “premature” and said the United States would seek other means to support the agency, though he did not offer specifics.

The United States argues that United Nations agencies should wait for a resolution of the Palestinians’ application for full membership in the United Nations as a whole. Palestinian statehood should emerge from negotiations with Israel, not from acts by third parties or international groups, Washington argues; otherwise United Nations membership will change little for Palestinians on the ground.

Arab diplomats say that the American position is a bit disingenuous, since Washington has maneuvered to try to prevent the Palestinians from getting the necessary 9 votes in the 15-seat Security Council, and would use its veto there if they did. The announcement on Monday by Bosnia, which currently has a seat on the Council, that it would abstain appeared to deny the Palestinians the chance for nine yes votes, making an American veto appear unnecessary.

At Unesco, though, no country has a veto.

Mr. Killion said in a statement that “there are no shortcuts” to a Palestinian state and that “we believe efforts such as the one we have witnessed today are counterproductive.” Last week, Secretary of State Hillary Rodham Clinton called the Unesco application “inexplicable.”

Both parties in Congress denounced the Unesco action on Monday. Representative Nita M. Lowey, Democrat of New York, called it “counterproductive,” saying in a statement that “Unesco is interfering with the prospects for direct negotiations between Israel and the Palestinians.” Ileana Ros-Lehtinen, the Florida Republican who heads the House Foreign Affairs Committee, characterized the Unesco move as “anti-Israeli and anti-peace” and called for a quick cutoff of funds.

There has been some discussion of Arab nations contributing more to Unesco to make up the budget shortfall, but nothing has been promised. And the Unesco bylaws seem to require that extra funds contributed to the group cannot be used for its operating budget.