Mr. Netanyahu has angered his most important ally, Mr. Trump, who has publicly derided him, accused Israel of using excessive force in pursuing its war aims and suggested that it is undermining the deal with Iran.

The memorandum signed this week by Mr. Trump and Iran’s president, Masoud Pezeshkian, provides for a 60-day window to negotiate a long-term peace pact addressing matters like limiting Iran’s nuclear program and major financial incentives, including the lifting of Western sanctions to aid Iran’s battered economy. Iran’s supreme leader, Ayatollah Mojtaba Khamenei, said that he assented to the deal but did not agree with it and placed the responsibility for it on Mr. Pezeshkian, warning against bowing to American demands.

Talks for that long-term agreement were expected to begin on Friday at a resort on Lake Lucerne, in Switzerland. But diplomats said the Iranians withdrew from the planned meeting, and Vice President JD Vance, who was scheduled to take part, abruptly canceled his trip late Thursday night in Washington, Friday morning in Europe. Neither side, nor the countries that have acted as intermediaries, have said when the negotiations might take place.

Dana Stroul, a former top Pentagon official for the Middle East in the Biden administration, said the delay suggests American misunderstanding of Iranian leaders, for whom salvaging their country’s economy is not the top priority.

Ms. Stroul, now a senior fellow at the Washington Institute for Near East Policy, said that given the widening rift between Washington and Jerusalem, “Tehran smells blood in the water, and they’re trying to stir the pot and further drive a wedge because they anticipate that everyone will blame Israel.”

The fighting in Lebanon, intimately tied to conflict between Iran and Israel, has long been a string of retaliations, with Israel consistently using far greater force and Lebanon suffering far greater destruction and casualties. The latest chapter began after Israel and the United States started bombing Iran, Hezbollah’s sponsor, on Feb. 28. Hezbollah responded with rocket and drone fire into Israel, which retaliated with airstrikes and a ground invasion.

Abdi Latif Dahir and Euan Ward reported from Beirut, Lebanon, Adam Rasgon from Jerusalem and Johnatan Reiss from Tel Aviv. Reporting was contributed by Erica L. Green, Erika Solomon, Michael Crowley, Ronen Bergman, Jim Tankersley, Yeganeh Torbati, Pranav Baskar, Sanam Mahoozi, Jenny Gross, Ephrat Livni and Alan Yuhas.