A new cease-fire proposal circulates at the U.N., driven by outrage over Israel’s strike on a tent camp.

Seeking to harness the outrage over an Israeli strike on Sunday that set fire to an encampment and killed least 45 displaced Palestinians, including children, many diplomats at the United Nations Security Council are backing a new resolution this week that would demand an immediate cease-fire and a halt to Israel’s military operations in the city of Rafah.

But they will have to overcome the objections of the United States, which has veto power on the Council and has signaled it will not support the resolution in its current form.

Algeria, the only Arab representative in the current makeup of the Security Council, drafted and circulated the one-page resolution, which says that “Israel, the occupying Power, shall immediately halt its military offensive, and any other action in Rafah.” It calls for “an immediate cease-fire respected by all parties, and also demands the immediate and unconditional release of all hostages.”

The Council held back-to-back meetings on the war in Gaza on Tuesday and Wednesday, first an emergency session behind closed doors about the strike on the encampment in Rafah and then a scheduled monthly open meeting on the Israeli-Palestinian conflict. Algeria’s resolution was expected to go to a vote in the coming days.

“The human cost is self-evident and appalling,” said Algeria’s ambassador, Amar Bendjama, told the Council on Wednesday. “These crimes speak for themselves.”

One U.S. official, who spoke on condition of anonymity because he was not authorized to speak publicly, said the United States would block the current version of the resolution, which it views as unbalanced and problematic. He said that the United States had proposed a number of revisions.

In particular, the official said, the United States does not want to endorse a resolution that calls on Israel to completely halt its military offensive in Rafah, which Israeli commanders maintain is still a stronghold for the armed group Hamas. The Biden administration supports limited Israeli operations there.

As one of the five permanent members of the Council, the United States holds veto power and has wielded it against three previous cease-fire resolutions since the war started in October. In March, the United States allowed a resolution to pass that called for a humanitarian cease-fire for the month of Ramadan by abstaining from the vote.

In recent weeks, as the civilian toll in Gaza has mounted, U.S. officials have become more openly critical of Israel’s conduct of the war. At least 36,000 people have been killed in the Israeli bombardment and ground operations, according to Gazan Ministry of Health, which does not differentiate between fighters and civilians in its count. Health officials have said a majority of the people killed are women, children and other noncombatants.

Gazan authorities say at least 45 people were killed in Sunday’s strike and its fiery aftermath as a fire tore through the Kuwait al-Salaam camp, where displaced people were living in tents. Among the casualties was a toddler whose burned and headless body was shown in a video verified by The New York Times.

“The continued pattern of significant civilian harm resulting from incidents like Sunday’s airstrikes undermines Israel’s strategic goals in Gaza,” Robert A. Wood, the U.S. deputy ambassador to the United Nations, told the Council on Wednesday. Mr. Wood added Israel had the right to defend itself but also had “obligations to protect civilians.”

On Tuesday, senior Biden administration officials expressed horror over Sunday’s strike but said that it was not a part of a major ground operation and so did not cross President Biden’s red line for withholding weapons shipments to Israel.

The Algerian resolution also cites an emergency ruling last Friday by the United Nation’s top court, the International Court of Justice in The Hague. The ruling ordered Israel to immediately halt its military operation in Rafah, though Israeli officials have argued its wording left some room for interpretation. The ruling came after arguments by South Africa, which late last year brought a case accusing Israel of genocide to the court.

Several Security Council diplomats said that they hoped to vote on the resolution soon to capture the momentum and outrage generated by the Sunday night strike and to prevent, if possible, harm to more civilians in Gaza. Drawn-out negotiations to appease the United States, the diplomats said, would send the wrong signal about the Council’s resolve to take action.

“This Council must express itself urgently on the situation in Rafah and demand an end to this offensive,” France’s ambassador, Nicolas de Rivière, said.