Donald J. Trump’s election victory is plunging efforts to reach a cease-fire in Gaza into further uncertainty, after a year of failed attempts by the Biden administration foundered because of irreconcilable demands from Israel and Hamas.

For months, leaders across the region — in Israel, Lebanon, Gaza and Qatar — have taken a wait-and-see approach to the U.S. election. It is unclear what will come next, but any firm advancement on a cease-fire, if there is one at all, would likely be delayed until after Mr. Trump’s inauguration in January, analysts said.

The sense was that President Benjamin Netanyahu of Israel “was waiting for the results of the U.S. presidential election to make a move,” said Michael Stephens, a Middle East expert at the Royal United Services Institute, a London-based research group. “Why would he give Biden anything now?”

More than 42,000 people have been killed in Gaza since the war began, including thousands of women and children, according to local Palestinian health officials. The war was triggered by the Hamas-led attack last October in which roughly 1,200 people in Israel were killed and 250 taken hostage.

The Biden administration had urged both sides to bridge their remaining differences and agree to a three-stage truce. As part of the proposed accord, the phases would see Israel end the war against Hamas, withdraw from Gaza, and release Palestinian prisoners; Hamas would free the 101 hostages still held there. (Proposals for a short-term truce were rejected by Hamas, which demanded an end to the war as a condition for agreeing to a deal.)

Mr. Netanyahu has welcomed the election of Mr. Trump, who was a staunch defender of Israel during his first term. He was one of the first to congratulate Mr. Trump on his victory, and spoke to him on Wednesday evening. The two agreed “to work together for the sake of Israel’s security,” according to a statement from the Israeli prime minister’s office.