President Trump said on Thursday in a social media post that the Board of Peace, an organization the administration established to oversee a Gaza cease-fire, had reached an agreement for Hamas to begin disarming in the Gaza Strip.

There was no immediate comment from Hamas or Israel. The Board of Peace said Thursday evening that Hamas had agreed to a “detailed road map” on disarmament of its forces and Israeli withdrawal from Gaza.

“For the first time, Hamas officially has committed to an actionable plan for relinquishing all its weapons, which will be followed by Israeli withdrawal,” the board said in a statement on social media.

Mr. Trump hailed the plan as “a critical step towards Gaza finally being governed by a new Palestinian government that will work closely with the Board of Peace to help the Palestinian people.” He added: “At the same time, Israel will have the security it deserves, with Gaza no longer used as a base for terror attacks.”

In a call with reporters held shortly after the president made his post, a senior Trump adviser involved in the negotiation effort said that the process for disarmament would happen over a matter of weeks.

Officials on the board who spoke to reporters repeatedly emphasized that the process would take time. They said that the Israelis were skeptical that Hamas would give up their arms and relinquish any government involvement in Gaza.

Nickolay E. Mladenov, a senior official in the talks, said on social media that the agreement “took months of very difficult negotiations.” He added: “What the agreement says matters. What happens next matters even more. Implementation and verification have to be real. Withdrawal must move in lockstep with decommissioning.”

The total disarmament and demilitarization of Gaza is a core demand by Israel, which the Board of Peace plan seeks to address. But many members of Hamas view any such deal as surrender.

In April, two Hamas officials told The New York Times that the group was prepared to relinquish some automatic rifles and other arms belonging to its police force and security services in Gaza, but that concession fell short of Israeli-U.S. demands.

Experts estimate that Hamas’s military wing has many more weapons than its police force, including tens of thousands of automatic rifles and heavier weapons like anti-tank rockets.

Jonathan Harounoff, who recently stepped down as Israel’s international spokesman at the United Nations, said that the complete disarmament of Hamas had been the “primary obstacle” to reconstruction efforts in Gaza, and that Hamas had broken commitments before.

Israel has been clear, he added, that “full demilitarization of the Gaza Strip” was a “non-negotiable” precondition for any withdrawal of Israeli forces. Mr. Trump, in his social media post, said the agreement would happen in “structured phases,” and that “as disarmament is completed, Israeli forces will withdraw.”

Talks involving Hamas, the Board of Peace and Israel had been deadlocked over the next steps in the October cease-fire that was supposed to end the war in Gaza, which began nearly three years ago.

Hamas led an assault on Israel on Oct. 7, 2023, that killed about 1,200 people, with some 250 taken hostage, according to the Israeli authorities. The subsequent Israeli military campaign ravaged the Gaza Strip, killing more than 70,000 people, according to Gaza health officials.

Natan Odenheimer and Adam Rasgon contributed reporting.