When Benny Gantz, a member of Israel’s war cabinet, met David Cameron, Britain’s foreign secretary, in London on Wednesday, he got a sharp message that Israel must do more to allow humanitarian aid to flow into Gaza.
It was the kind of minister-level meeting that would normally draw modest attention amid the flurry of high-level diplomacy that has enveloped the Israel-Hamas war. But Mr. Gantz and Mr. Cameron are no mere functionaries.
Mr. Gantz, a former chief of staff of the Israel Defense Forces, is a popular political rival of Prime Minister Benjamin Netanyahu, and Mr. Netanyahu expressed deep displeasure at what he viewed as an unsanctioned trip by a would-be Israeli leader.
Mr. Cameron, a former prime minister, has enjoyed uncommon latitude as foreign secretary, speaking out forcefully on issues like Gaza and the war in Ukraine on international trips, where he is often treated as though he were still in his old job.
The unusual optics of the meeting — almost two shadow leaders — speak to the peculiar domestic politics in each country. Israel is in the grip of a devastating war that has pulled Mr. Netanyahu and Mr. Gantz into a temporary alliance. Britain is in the twilight stages of an era of Conservative-led governments, with a prime minister, Rishi Sunak, who is more occupied with a general election later this year than with foreign policy.
For Britain, diplomats and experts said, deploying Mr. Cameron to deliver a tough message to Israel is valuable because it will register more than if it came from a standard-issue cabinet minister. It also spares Mr. Sunak the political risk of pressing Mr. Netanyahu directly and potentially being rebuffed.
“Cameron is a big beast, relatively speaking,” said Daniel Levy, a former Israeli peace negotiator who now runs the U.S./Middle East Project, an institute in London and New York. “They would want Gantz to know how desperate the humanitarian situation has become, just what a strain it is placing on the relationship and how difficult it is going to be to keep going like this.”
In the meeting, Mr. Cameron said in a statement, he and Mr. Gantz discussed efforts to pause the fighting, and Mr. Cameron urged him to increase aid. While he said that Britain supports Israel’s right to self-defense, “as the occupying power in Gaza, Israel has a legal responsibility to ensure aid is available for civilians.”
“That responsibility has consequences,” Mr. Cameron added, “including when we as the U.K. assess whether Israel is compliant with international humanitarian law.”
Mr. Gantz also met with Britain’s national security adviser, Tim Barrow, a session that was joined by Mr. Sunak, according to a readout from Mr. Gantz’s office.
Giving Mr. Gantz these meetings also sends a message to Mr. Netanyahu. The prime minister has frustrated officials in London and Washington with his refusal to pause the military campaign or agree on terms for a hostage deal with Hamas, not to mention his dismissal of a future peace accord with the Palestinians.
There are tensions within the war cabinet over some of these issues as well. Mr. Gantz has at times aligned with another former top military commander, Gadi Eisenkot, against Mr. Netanyahu, according to Israeli analysts. That is complicated by the fact that Mr. Gantz is viewed as a rival to the prime minister in a future election.
“Gantz and Eisenkot have openly disagreed with Netanyahu over the terms of a Hamas hostage deal,” Mr. Levy said. “I imagine the British gently prodded to understand what the dynamics at home are.”
For now, Mr. Gantz, 64, has higher approval ratings than Mr. Netanyahu, who was haunted by legal troubles before the war and is blamed by many Israelis for the intelligence failures in the Oct. 7 attack by Hamas fighters. A recent poll by Channel 13, an Israeli TV broadcaster, showed that if elections were held today, Mr. Gantz’s centrist National Unity party would win 39 seats in the Knesset, Israel’s parliament, while Mr. Netanyahu’s right-wing Likud would win only 17 seats.
Before stopping in London, Mr. Gantz visited Washington, where he met on Monday with Vice President Kamala Harris, Secretary of State Antony J. Blinken and the national security adviser, Jake Sullivan, but not — as some Israeli journalists speculated beforehand — with President Biden.
Mr. Gantz told Mr. Netanyahu about his plans to fly to the United States to coordinate the messages he would convey in his meetings with American officials, according to a statement from his office. Mr. Netanyahu nevertheless expressed his displeasure, and Mr. Gantz made the trip without diplomatic support.
In Washington as in London, the most pressing issue was the halting flow of humanitarian aid. Ms. Harris pushed for a pause in the fighting in Gaza, according to the White House, and urged the Israeli government to do more to allow aid to reach those in need in Gaza.
“Kamala Harris, in particular, is playing to the progressives and Arab Americans by highlighting her defense of the Palestinians in Gaza,” said Martin S. Indyk, a former American ambassador to Israel. “I think he got the message, and we’ll see Israel do more, hopefully a lot more, to get the aid flowing.”
If Ms. Harris is viewed as being a proponent for the Palestinians inside the Biden White House, Mr. Cameron plays a similar role in the British government. Last month, during a visit to the Falkland Islands, he said Israel should focus on a cease-fire “right now,” rather than a military offensive in Rafah, a city in the south of Gaza that has become a refuge for fleeing Palestinians.
Speaking in the House of Lords on Tuesday, Mr. Cameron gave vent to the frustration of British officials over the sluggish pace of aid. He warned that the civilians trapped in Gaza faced the real prospect of famine and disease.
“We’ve had a whole set of things we’ve asked the Israelis to do, but I have to report that the amount of aid they got in February was about half what they got in January,” Mr. Cameron said. “So, patience needs to run very thin, and a whole series of warnings need to be given, starting with the meeting I have with Minister Gantz.”
Mr. Cameron’s blunt words have occasionally caused problems, according to critics. Last month, for example, he said Britain might consider recognizing a Palestinian state even before peace negotiations between the Palestinians and Israel. That angered Israelis and helped precipitate a vote in the Knesset, in which 99 members voted against any unilateral recognition of a Palestinian state.
Mr. Sunak later clarified that there had been no change in British policy, which is to pursue a two-state solution to the conflict. The United States also favors a Palestinian state that would result from a negotiated settlement with Israel.
Mr. Indyk, the former ambassador, said the Knesset vote enabled Mr. Netanyahu to say to the Biden administration that there is “wall-to-wall opposition to a Palestinian state, on the basis of something the administration had no intention of doing.”