JERUSALEM — Israel’s Defense Ministry has promoted a plan to force much the population of the Gaza Strip into a small and largely devastated zone in the territory’s south, a proposal that threatens to derail the latest efforts to forge a truce between Israel and Hamas.

In recent weeks, Israeli officials have briefed journalists and foreign counterparts on a loose plan to force hundreds of thousands of Palestinian civilians into an area controlled by Israel’s military close to the Gaza-Egypt border. Legal experts have warned that the plan would violate international law because the civilians would be barred indefinitely from returning to their homes in other parts of Gaza, a restriction that would constitute a form of ethnic cleansing.

While the Israeli government has yet to formally announce or comment on the plan, the idea of a new encampment in southern Gaza was first proposed last week by Israel Katz, the Israeli defense minister. He discussed it at a briefing with Israeli correspondents who focus on military affairs, and The New York Times reviewed readouts of the briefing written by its attendees. Several attendees also wrote articles that attracted widespread attention among both Israelis and Palestinians.

A spokesperson for Katz declined to comment on the reports, as did the office of Benjamin Netanyahu, Israel’s prime minister.

Now, Hamas has cited Katz’s proposal as one of the latest obstacles to a new truce. During a ceasefire, in exchange for releasing roughly 25 hostages, Hamas wants Israeli troops to withdraw from much of Gaza. The new Israeli plan makes such an outcome far less likely, since it would ensure that Israeli troops remained in charge of a large area over which Hamas seeks to reestablish control.

Husam Badran, a senior member of Hamas, described the establishment of the encampment as a “deliberately obstructive demand” that would complicate the fraught negotiations.

“This would be an isolated city that resembles a ghetto,” Badran said Monday in a text message. “This is utterly unacceptable, and no Palestinian would agree to this.”

Hopes for an imminent truce rose last week after Netanyahu went to Washington for meetings with President Donald Trump that many expected would result in an Israeli compromise. Instead, Netanyahu — who has previously slow-walked negotiations for personal and political reasons — returned to Israel without a breakthrough.

The negotiations remain stuck on issues, including the permanence of any truce: Israel wants to be able to return to war, while Hamas wants guarantees that any ceasefire would evolve into a full cessation of hostilities. Israel also wants Hamas to commit to disarmament, an idea that the militant group has rejected. There are also disagreements over how aid will be delivered during a truce.

According to some of the readouts of the briefing by Katz, the defense minister described the proposed new encampment as a “humanitarian city” that would, at first, house at least 600,000 Palestinians. Katz said it would later hold the entire population of Gaza, or roughly 2 million people, according to the readouts and reports.