Diplomatic efforts pick up to avert Israel, Hezbollah war

U.S. and Middle East diplomats worked Sunday to keep the fighting between Israel and Hezbollah from spiraling into a full-scale war, as the Druze community in the Israeli-controlled Golan Heights began to bury the 12 children and teenagers killed by a rocket fired from Lebanon.

Israel has accused the Lebanon-based Hezbollah of carrying out the deadly strike on Saturday and threatened a strong response. The Israeli cabinet is meeting later Sunday to discuss its course of action, hours after Prime Minister Benjamin Netanyahu returns from his visit to Washington.

Hezbollah said it had nothing to do with the deaths but claimed responsibility for a series of other attacks in the area on Saturday, including launching a Falaq-1 rocket at an Israeli military site a few kilometers from the strike scene. Israel’s military said that an Iranian-made Falaq-1 hit the soccer field on which the children and teenagers were playing, and that it was launched from the vicinity of Chebaa, a southern Lebanese village.

U.S. officials have reached out to their counterparts in Israel and Lebanon and also traded messages with Iran, which backs Hezbollah, to try to de-escalate the tensions, according to Arab and European officials familiar with the matter. All sides have indicated they aren’t interested in widening the conflict, but chances of a miscalculation remain high.

The Saturday strike also injured around 40 people, according to the Israeli Prime Minister’s Office. The rocket carried a 50-kilogram warhead, an unusually heavy payload, Israel’s military said.

“We are approaching the moment of an all-out war against Hezbollah and Lebanon,” Israeli Foreign Minister Israel Katz said shortly after Saturday’s strike. The attack “crossed all red lines, and the response will be in accordance.”

The Israeli military already struck several targets deep into Lebanon on Sunday morning in immediate response to the attack, which the military said was the single largest civilian casualty event since Oct. 7, when Hamas killed 1,200 people and took 250 hostage from southern Israel, according to local authorities, and triggered the continuing war in Gaza. Gaza health authorities say 39,000 people have been killed in the war, most of them civilians. The figure doesn’t specify how many were combatants.

The strike comes at a critical time for U.S.-led efforts to strike a cease-fire deal in Gaza. An escalation between Israel and Hezbollah could disrupt those negotiations, which have been stalled for months but are set to resume this week in Rome. Top officials are planning to attend the latest round of talks, including CIA Director William Burns, Israeli spy chief David Barnea, Egyptian intelligence chief Abbas Kamel and Qatari Prime Minister Mohammed bin Abdul Rahman al-Thani, people familiar with the matter said.

Israel and Hezbollah have been trading cross-border fire exchanges since the U.S.-based terrorist organization joined the fight, and Hezbollah has said it wouldn’t agree to a cease-fire until fighting ends in Gaza.

Saturday’s strike has dialed up the risk that the slow-burning conflict between Israel and Hezbollah could trigger a full-scale war. For months, the two sides have managed to keep the conflict within limits and avoided an all-out war that could be devastating for both Israel and Lebanon.

The strike was exactly the kind of incident that regional officials and observers have feared for months: a miscalculation that could generate domestic pressure on the other side to respond forcefully.

“We’ve always said that something like this is possible, that there is an attack that kills civilians for instance or in other ways creates a situation on one side that this party feels compelled to strike back very hard,” said Heiko Wimmen, project director for Lebanon, Syria and Iraq at the International Crisis Group.

“We’re going to get a higher level of violence, and that means almost by definition the risk of something like that happening again, that the risk of escalation increases,” he said.

The attack amplifies pressure on the Biden administration, which has sought for months to de-escalate the fighting on the Israel-Lebanon border and prevent the Gaza war from spiraling into a wider regional conflict. The war has also provoked attacks by Yemen’s Houthi rebels on vital Red Sea shipping lanes and on Israel, along with attacks by Iranian-backed militia groups on U.S. forces in Iraq and Syria.

The U.S. National Security Council condemned the Saturday strike, and said Washington’s support for Israel remains firm as it continues to push for a diplomatic solution.

“Israel continues to face severe threats to its security, as the world saw today, and the United States will continue to support efforts to end these terrible attacks along the Blue Line, which must be a top priority,” read a statement from an NSC spokesperson, referring to the United Nations-recognized demarcation line between Israel and Lebanon. “Our support for Israel’s security is iron-clad and unwavering against all Iranian backed terrorist groups, including Lebanese Hezbollah.”

—Benoit Faucon, Dov Lieber, Aresu Eqbali and Ken Thomas contributed to this article

Write to Summer Said at summer.said@wsj.com and Jared Malsin at jared.malsin@wsj.com