Switzerland said US talks with Iranian negotiators on a pact to end the Middle East conflict would not take place on Friday, while Vice President JD Vance dropped plans to travel there, fuelling uncertainty whether a lasting truce can be found.
"The logistics of these negotiations have never been simple or predictable," a White House spokesperson said in a statement.
Vance and the US delegation had been ready to depart for the talks, set for the Swiss mountaintop resort of Burgenstock, as soon as plans were finalised.
A Swiss foreign ministry statement said the talks had been postponed. Switzerland remains ready to facilitate these talks and the relevant preparatory work at Burgenstock is continuing, the statement added.
There was no immediate response from Iran, which had said it was ready to begin technical talks after Wednesday's 14-point accord extended a tenuous ceasefire by at least 60 days.