The Palestinian Authority’s leader assails the U.S. veto of a U.N. cease-fire resolution.

Criticism of a U.S. veto of a United Nations Security Council resolution for an immediate cease-fire in Gaza grew on Saturday, with rights groups and aid organizations warning that the move would prolong the suffering in the enclave and the leader of the Palestinian Authority issuing a strong condemnation.

Mahmoud Abbas, the president of the Palestinian Authority — which Washington and others have floated as a potential governing body for post-war Gaza — called the United States “aggressive and unethical” and said the veto was “a mark of shame that will follow the United States for many years.”

Although Biden officials have said that Israel must do more to limit civilian casualties and allow humanitarian aid into Gaza, frustration has grown among some U.S. allies as Washington continues to stand behind Israel despite a rising civilian death toll and increasing desperation as aid remains insufficient.

Officials across the Middle East have been urging an immediate stop to Israel’s offensive, with Jordan’s foreign minister, Ayman Safadi, calling it a “massacre” at a news conference in Washington on Friday.

Hours after the United States blocked the resolution for an immediate cease-fire, Secretary of State Antony J. Blinken and an Arab delegation said early Saturday that they had discussed efforts to ease the humanitarian crisis in Gaza during a meeting in Washington.

Mr. Blinken said he had discussed “our shared goal of establishing a future Palestinian state alongside Israel” during a meeting on Friday with ministers from Arab nations and representatives for the Palestinian Authority. He did not mention a cease-fire.

In a statement, Qatar, which was part of the Arab delegation meeting with Mr. Blinken, reiterated calls among the group for an immediate cease-fire and renewed their “rejection” of Israel’s military operations in Gaza.

Israel’s ambassador to the United Nations, Gilad Erdan, thanked the United States for its veto. Before the vote, he had made the case that a cease-fire would allow Hamas to regroup and plan more attacks. Israel began its airstrikes and ground invasion of Gaza in response to Hamas’s attack on Oct. 7, in which Israel says 1,200 people were killed.

Rights groups and aid organizations immediately criticized the U.S. veto. The United Nations has warned that Gaza is on the brink of a total breakdown in social order as its 2.2 million civilians are pushed to the limit of survival.

“By vetoing this resolution, the U.S. stands alone in casting its vote against humanity,” Avril Benoit, the executive director of Doctors Without Borders in the United States, said in a statement on Friday. “The U.S. veto makes it complicit in the carnage in Gaza,” she added.

Louis Charbonneau, the United Nations director for Human Rights Watch, said in a post on the social media site X that by providing Israel with “diplomatic cover,” “the U.S. risks complicity in war crimes.”

John F. Kirby, the strategic communications coordinator at the White House National Security Council, on Friday defended U.S. efforts to pressure Israel to be more precise in its strikes, which have killed more than 15,000 people in Gaza in two months of war, according to the Gaza health ministry.

Although he said that the administration would continue working with Israeli counterparts to limit harm to civilians in Gaza, Mr. Blinken said a day earlier that there remained “a gap” between Israel’s stated intent to protect civilians and the events playing out in Gaza.

The United States argued that a cease-fire would leave Hamas in place and that Israel had a right to defend itself. The U.N. Security Council’s 13 other member states voted for it, save for Britain, which abstained.

Hamas condemned the U.S. veto, saying that the vote made the Biden administration “an accomplice in the killing of our people through the political and military support of the occupation.”