Swiss officials on Friday announced that the first round of negotiations between the U.S. and Iran, scheduled to be held at the mountaintop resort of Bürgenstock, had been postponed until further notice. 

The Swiss Foreign Ministry said in a statement that Switzerland is still ready to facilitate negotiations between the two nations, adding that “preparatory work” for the talks continues. 

However, Swiss officials provided no details about why the talks were called off or when they may be rescheduled. 

The U.S.-Iran memorandum of understanding, signed electronically on Wednesday, provides a 60-day ceasefire window during which time both sides are directed to sit down for in-depth negotiations over Iran’s nuclear program, its support for proxies and sanctions relief. 

Vice President J.D. Vance was scheduled to fly to the Bürgenstock Resort on Friday for what was originally a signing ceremony for the agreement. But Mr. Vance abruptly canceled the trip late Thursday evening. 

A White House spokesperson cited logistical issues as the primary reason the talks were called off. 

“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,” the spokesperson wrote in a statement. “But the logistics of these negotiations have never been simple or predictable. As of now the Vice President is not departing tonight.”

The delay comes after Israel launched airstrikes across southern Lebanon on Friday, killing at least 18 people and adding pressure on the U.S.-Iran agreement.  

Some reports on Friday said Iran had decided to pull out of the talks following Israel’s attacks on Lebanon.

Iran has insisted for weeks that Israel’s continued airstrikes against Hezbollah in Lebanon violate the agreement, which calls for a ceasefire on all fronts of the war.