A top Israeli Cabinet minister headed to Washington on Sunday for talks with American officials, sparking a rebuke from Prime Minister Netanyahu, according to an Israeli official, in a sign of widening cracks in Israel’s wartime government nearly five months into its war with Hamas.

The trip by Benny Gantz, a centrist political rival who joined Mr. Netanyahu’s hard-line government in the early days of the war following Hamas’ October 7 attack on southern Israel, comes amid deep disagreements between Mr. Netanyahu and President Biden over how to alleviate the suffering of Palestinians in Gaza and create a post-war vision for the enclave.

The United States was prompted to airdrop aid into Gaza on Saturday after dozens of Palestinians rushing to grab food from trucks were killed last week. The airdrops circumvent what’s been a prohibitive aid delivery system, which has been hobbled by Israeli restrictions, logistical issues within Gaza as well as the fighting inside the tiny enclave. Aid officials say the airdrops are far less effective than the aid sent via trucks.

American priorities in the region have increasingly been hampered by Mr. Netanyahu’s hard-line Cabinet, where ultranationalists dominate. Mr. Gantz’s more moderate party at times acts as a counterweight to Mr. Netanyahu’s far-right allies.

An official from Mr. Netanyahu’s Likud party said Mr. Gantz’s visit was without authorization from the Israeli leader. The official said Mr. Netanyahu had a “tough talk” with Mr. Gantz about the trip and told him the country has “just one prime minister.”

An Israeli official said Mr. Gantz had informed Mr. Netanyahu of his intention to travel to the United States and to coordinate messaging with him. The official said the visit is meant to strengthen ties with Washington, to bolster support for Israel’s ground campaign, and to push for the release of Israeli hostages held in Gaza.

Mr. Gantz is set to meet with Vice President Harris and national security adviser Jake Sullivan, according to his National Unity party.

Both officials spoke on condition of anonymity because they weren’t authorized to discuss the dispute with the media.

Mr. Netanyahu has tanked in popularity since the war broke out, according to most opinion polls, with many Israelis holding him responsible for Hamas’ terrorist attacks.

Critics say Mr. Netanyahu’s decision-making has been tainted by political considerations, a charge he denies. The criticism is particularly focused on plans for postwar Gaza. Mr. Netanyahu has released a proposal that would see Israel maintain open-ended security control over the territory with local Palestinians running civilian affairs.

The United States wants to see progress on the creation of a Palestinian state, envisioning a revamped Palestinian leadership running Gaza with an eye toward eventual statehood.

That vision is opposed by Mr. Netanyahu and the hard-liners in his government. Another top Cabinet official from Mr. Gantz’s party has questioned the handling of the war and the country’s strategy for freeing the hostages.

Mr. Netanyahu’s government, Israel’s most conservative and religious ever, has also been rattled by a court-ordered deadline for a new bill to broaden military enlistment of ultra-Orthodox Jews, many of whom are exempted to pursue religious studies. The issue has come up as hundreds of Israeli soldiers have been killed since October 7 and the military is looking to fill its ranks as the war drags on.

Mr. Gantz, who polls show would earn enough support to become prime minister if a vote were held today, is viewed as a political moderate. But he has remained vague about his view of Palestinian statehood.

A visit to America, if met with progress on the hostage front, could further boost Mr. Gantz’s support. Israel has essentially endorsed a framework of a proposed Gaza  cease-fire and hostage release deal, and it is now up to Hamas to agree to it, a senior American official said Saturday.

Israelis, deeply traumatized by Hamas’ attack, have broadly backed the war effort as an act of self-defense, even as global opposition to the fighting has increased.

But a growing number are expressing their dismay with Mr. Netanyahu. Some 10,000 people protested late Saturday to call for early elections, according to Israeli media. Such protests have grown in recent weeks, but remain much smaller than last year’s demonstrations against the government’s judicial overhaul plan.

If the political rifts grow and Mr. Gantz quits the government, the floodgates will open to broader protests by a public that was already unhappy with the government when Hamas struck, said Reuven Hazan, a professor of political science at Jerusalem’s Hebrew University.

“There is a lot of anger,” he said, listing grievances that were building well before October 7. “The moment you have that anger and a coalition that is disconnected from the people, there will be fireworks.”

Mr. Netanyahu’s government won’t collapse if Mr. Gantz exits, but it could lose legitimacy in the eyes of much of the public.

Talks aimed at brokering a Gaza cease-fire restarted Sunday in Egypt. International mediators hope to broker a deal that would pause the fighting and free some of the remaining hostages before the Muslim holy month of Ramadan begins around March 10.