Negotiators from Israel and Hamas have agreed to a cease-fire in Gaza after more than 15 months of devastating war, officials said on Wednesday.

The agreement needs to be formally ratified by the Israeli cabinet, two senior Israeli officials said. In the run-up to the deal, officials said there was last-minute wrangling over the Egypt-Gaza border, which Israeli forces currently control.

The office of Benjamin Netanyahu, the Israeli prime minister, said in a statement that a number of clauses in the agreement still remained unresolved, but that it was hoped that they would be worked out on Wednesday night.

The cease-fire would take effect immediately, according to a White House official. Its first phase will last six weeks, and hostages will start being released during that phase, though it was not clear when that could begin. The official spoke on the condition of anonymity because of the sensitivity of the deal.

If implemented, the cease-fire would allow for the release of Israeli hostages held in Gaza and Palestinian prisoners in Israel, after over a year of war that has killed tens of thousands of Palestinians and destroyed much of the enclave.

Basem Naim, a Hamas official, confirmed the agreement, although the Palestinian militant group had yet to release a formal statement.

President-elect Donald J. Trump also announced that a hostage deal had been reached, writing on social media that “THEY WILL BE RELEASED SHORTLY.” Mr. Trump had threatened severe consequences unless Israel and Hamas reached an agreement before his Jan. 20 inauguration, which some officials credited with helping to advance the negotiations.

The nearly uninterrupted fighting in Gaza has left Hamas severely battered, with many of its military commanders killed, including its longtime leader in Gaza, Yahya Sinwar, who was killed by Israeli forces in September.

Neither Israel nor Hamas had publicly endorsed the agreement, but the Palestinian group said on Tuesday that the negotiations had entered their “final stages,” and Israel’s foreign minister, Gideon Saar, said on Wednesday evening that he was returning early from a trip abroad to join cabinet discussions about the hostages. Hamas said in a statement on Wednesday evening that it had responded to the proposed deal, without clarifying further.

In order to implement the deal, Hamas’s negotiating team at the talks in Doha, Qatar, had to obtain the consent of the group’s commanders in Gaza, including Muhammad Sinwar, the brother of the commander killed by Israel in October.

Here’s what else to know:

• What’s in the deal: The cease-fire deal in Gaza is broadly similar to a three-phase framework publicized by President Biden in late May, according to several officials familiar with the talks. Under that proposal, Israel and Hamas would first observe a six-week cease-fire in which Hamas would release women, older men, and ill hostages in exchange for the release of Palestinians jailed by Israel, and 600 trucks carrying humanitarian relief would enter Gaza daily.
• Right-wing opposition: In Israel, some hard-line members of Prime Minister Benjamin Netanyahu’s government have also voiced opposition to the deal. But on Wednesday, Mr. Saar said he believed that a majority would sign off on an agreement if it came to a cabinet vote.
• Hostage talks: The deal on the table comes after months of shuttle diplomacy have failed to end the war in Gaza, which began after Hamas launched a surprise attack on Israel on Oct. 7, 2023, that killed 1,200 people and saw 250 taken hostage. Around 105 captives were later released in a weeklong cease-fire in November 2023 in exchange for 240 Palestinian prisoners.

Abu Bakr Bashir and Gabby Sobelman contributed reporting.