Israel and Gaza were in a state of disbelief mixed with relief on Saturday morning after Prime Minister Benjamin Netanyahu said Israel would cooperate with President Trump to end the war, following Hamas’s statement that it was ready to release all Israeli hostages.

The stunning turn of events on Friday — a Trump ultimatum to Hamas to accept his plan, a qualified Hamas acceptance, followed by a cautious Israeli agreement to proceed — held out the promise of an end to a devastating conflict just days before it reached the two-year mark.

It remained unclear how soon any concrete steps to end the conflict might be taken, however.

Hamas’s response to Mr. Trump said the group assented to releasing all Israeli hostages in accordance with the terms for ending the war outlined by the president in Washington on Monday, alongside Mr. Netanyahu. Those included calls for Israel to release 250 Palestinian prisoners serving life sentences and 1,700 others detained since the start of the war.

But Hamas also said that it required certain conditions on the ground to allow for the exchange of hostages and prisoners, and that it was ready to enter into indirect talks with Israel to discuss those conditions.

Hamas did not directly address the demands in Mr. Trump’s plan that it disarm. And it appeared to reject the plan’s insistence that Hamas play no role in the future governance of the enclave, saying that “other issues related to the future of Gaza and the Palestinian people’s authentic rights” would be “discussed in an inclusive Palestinian national framework that will include Hamas.”

Those caveats appeared to give Mr. Netanyahu pause. Only after 3 a.m. local time on Saturday — about five hours after Hamas’s response to the president — did his office issue a statement saying simply that Israel was ready for the “immediate release of all hostages.” It made no mention of Hamas’s conditions.

The statement added that Israel would cooperate with the White House “to end the war in accordance with the principles set forth by Israel that are consistent with President Trump’s vision.”

The Israeli military said it had instructed its commanders to “advance readiness for the implementation of the first phase of the Trump plan for the release of the hostages,” while reinforcing the need “for a rapid response to neutralize any threat.”