According to a White House official, the ceasefire would take effect immediately if finalized. The first phase would last six weeks and during this phase the release of hostages would begin. Because of the sensitivity of the deal, the officials spoke on condition of anonymity.

If implemented, the ceasefire would allow the release of Israeli hostages in Gaza and Palestinian prisoners in Israel. About 100 hostages are believed to remain in the Gaza Strip, although Israeli authorities believe about 35 of those people are dead.

Basem Naim, a Hamas official, confirmed the agreement, although the Palestinian militant group had not yet released a formal statement.

President-elect Donald J. Trump also announced that a hostage-taking agreement had been reached, writing on social media: “You will be released shortly.” Mr. Trump had threatened serious consequences if Israel and Hamas did not do so before his inauguration reached an agreement on Jan. 20, which some officials saw as helping move negotiations forward.

The almost non-stop fighting in Gaza has hit Hamas hard, killing many of its military commanders, including its longtime leader in Gaza, Yahya Sinwar, who was killed by Israeli forces last fall.

Neither Israel nor Hamas had publicly endorsed the deal, but the Palestinian group said on Tuesday that negotiations had entered their “final phase” and Israel’s foreign minister said on Wednesday evening that he was returning early from a trip abroad to take part in Cabinet talks about it the hostages take part.

Ahead of the deal, officials said there was a last-minute dispute over the border between Egypt and Gaza, which is currently controlled by Israeli forces.

To implement the deal, Hamas’s negotiating team had to seek approval from the group’s commanders in Gaza, including Muhammad Sinwar, the brother of the commander killed by Israel, at talks in Doha, Qatar.

Here’s what else you should know:

• What’s included in the deal?: According to several officials familiar with the talks, the Gaza ceasefire agreement is broadly similar to a three-tiered framework that President Biden released in late May. Under this May proposal, Israel and Hamas would initially observe a six-week ceasefire under which, in return for the release of Palestinians imprisoned by Israel, Hamas would release women, elderly men and sick hostages, and 600 trucks carrying humanitarian aid would enter Gaza daily.

• Right opposition: In Israel, some hardliners in Prime Minister Benjamin Netanyahu’s government have also spoken out against the agreement. But on Wednesday, Mr Saar said he believed a majority would approve a deal if it came to a cabinet vote.

• Hostage talks: The deal on the table comes after months of shuttle diplomacy to end the war in Gaza, which began when Hamas launched a surprise attack on Israel on October 7, 2023, killing 1,200 people and taking 250 hostage. Since Israel began its military campaign in response to the attack in October 2023, at least 45,000 Palestinians have been killed in Gaza, according to health authorities there.

Abu Bakr Bashir And Gabby Sobelman contributed to reporting.