The Buergenstock resort, in Obbuergen, where possible talks between the U.S. and Iranian delegations after the two countries' presidents signed an interim deal aimed at ending the war could take place, is seen from Lucerne, Switzerland, June 19. Reuters-Yonhap

WASHINGTON/DUBAI — Switzerland said U.S. talks with Iranian negotiators on a pact to end the Middle East conflict would not take place on Friday, as Vice President JD Vance dropped plans to travel to the country, adding to uncertainty whether a lasting truce can be found.

"The logistics of these negotiations have never been simple or predictable," the White House spokesperson said in a statement on Thursday night. Vance and the U.S. delegation had been ready to depart as soon as plans were finalised.

The talks, set for the mountaintop resort of Burgenstock, would not take place, Switzerland's foreign ministry confirmed, but gave no details.

There was no immediate response from Iran, which had earlier said it was ready to begin technical talks after Wednesday's 14-point accord extended a tenuous ceasefire by at least 60 days.