The Arab and Western officials who described Hamas’s supply situation all spoke on the condition of anonymity because they were disclosing information gleaned from human sources, communications intercepts and other streams of intelligence.

While the blockade has left Gaza’s roughly 2 million people scraping by with what little food and water they scrounge up, it does not yet appear to have begun to degrade Hamas’s ability to fight.

Israel has so far refused to allow any fuel to be delivered to Gaza, even as other aid begins to trickle in, leaving much of the enclave without electricity to power hospitals, desalinate or pump water, fire bakers’ ovens and run internet and cellphone services.

The United Nations, which handles the bulk of humanitarian relief work in Gaza, said on Thursday that it “has almost exhausted its fuel reserves and begun to significantly reduce its operations.”

Yocheved Lifshitz, 85, a freed hostage, said that while in captivity she ate the same single meal that Hamas fighters eat every day: pita bread with two kinds of cheese and cucumber.

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