Two regional officials, speaking to The Associated Press on condition of anonymity to discuss the closed-door talks, said mediators were focused on calming the fighting in Lebanon. 

One of the officials said Iran had suspended plans to begin direct talks with U.S. officials in Switzerland on Friday specifically over the fighting and comments by Israeli Prime Minister Benjamin Netanyahu, which they described as violating the interim deal between Iran and the U.S.

Vice President JD Vance on Thursday put off his trip to Switzerland, where he had been set to lead the next-phase talks with Iran provisioned by the memorandum of understanding signed by both countries on Wednesday. The White House blamed logistical issues for the delay in beginning the talks, which are expected to last 60 days.

President Trump said Thursday night he expected Hezbollah and Israel to stop fighting under the agreement struck between the U.S. and Iran.

"The United States is committed to PEACE, and we encourage everyone in the Middle East Region to maintain their commitment to allowing our negotiations to beautifully unfold," Mr. Trump said in a Truth Social post. "We expect a complete Ceasefire on all fronts, including Lebanon, Hezbollah, and Israel."  

Israel said it attacked Hezbollah in the early hours of Friday morning in response to "repeated violations of the ceasefire."  

In a brief statement the Israel Defense Forces said it had "struck throughout the night and continues to strike Hezbollah terrorists and infrastructure sites in several areas across southern Lebanon."

Lebanese officials said at least 18 civilians were killed, making it the deadliest attack since the U.S. and Iran reached an agreement early this week on the memorandum of understanding signed Wednesday by Mr. Trump and Iranian President Masound Pezeshkian.

Israel's military said Friday its forces struck targets throughout southern Lebanon overnight as Hezbollah reported intense fighting in the area.

Lebanon's state-run National News Agency reported at least 18 people were killed in Israeli airstrikes, which the Israeli military said were ongoing. Israel, meantime, said four of its soldiers had been killed in fighting in southern Lebanon, including a lieutenant colonel. An explosive drone attack hurt another five, it added.

Continued fighting in Lebanon could unravel the newly signed deal, which calls for an immediate halt to military operations "on all fronts, including in Lebanon," where Israel has been battling the Iran-backed Hezbollah militant group, and for ensuring Lebanon's "territorial integrity and sovereignty."

Vice President JD Vance is no longer planning to fly to Switzerland late Thursday to help kickstart talks with Iran, a White House spokesperson told reporters.

"As the Vice President said at his press conference, the plans for the upcoming technical talks have not been finalized, and the U.S. delegation has been prepared to depart at the first available opportunity. But the logistics of these negotiations have never been simple or predictable," the spokesperson said in a statement to the White House press pool. "As of now the Vice President is not departing tonight. We will let you know as soon as we have a concrete update about next steps."

The spokesperson added: "We look forward to beginning technical talks as soon as possible."

Under the memorandum of understanding signed by Iran and the U.S. this week, the two sides are planning to hold 60 days of technical talks on the fate of Iran's nuclear program. 

Earlier in the day, Vance told reporters the plan was for those talks to begin this weekend, and he intended to travel to Switzerland for the start of negotiations, but "that could change" because Iran is "not an easy country … to get out of."

"It just depends on exactly when the Iranians can get there," he said. "We're trying to figure that out as we speak, but again, I suspect it will happen this weekend."