Israel’s military said on Monday that it had expanded a humanitarian zone it created in southern Gaza. The move came just before the expiry of a Biden administration deadline for Israel to deliver more aid to the enclave or risk a cutoff of military supplies.

In a statement, the Israeli military said that the zone would now include field hospitals; tent compounds; shelter supplies; and provisions of food, water, medicine and medical equipment, though it did not specify whether any new additions had been made to the resources already present. The military provided a map showing that nine areas had been added to the zone.

Aid agencies have said that supplies are desperately needed to offset the humanitarian crisis in Gaza, especially in the north, where Israel has stepped up military operations against the militant group Hamas.

The Israeli military’s announcement came as the 30-day deadline set on Oct. 13 by the Biden administration is set to expire. In one of the starkest American warnings since the war began, the administration said that failure to provide more aid to Gaza’s 2.2 million residents before that deadline “may have implications for U.S. policy,” including on the provision of the military assistance upon which Israel depends.

The White House national security adviser, Jake Sullivan, said on Sunday that the United States would this week evaluate “what kind of progress” Israel had made on allowing aid into Gaza. Speaking on CBS’s “Face the Nation,” Mr. Sullivan said President Biden would then “make judgments about what we do in response.”