Officials in Switzerland said on Friday morning that the next stage of peace negotiations between the United States and Iran, focused on issues including Iran’s nuclear program and meant to begin on the shores of Lake Lucerne, had been postponed.

The announcement did not include any information about when the negotiations might now begin, raising immediate questions about the memorandum of understanding that President Trump and Iran’s president had signed earlier this week. That agreement left crucial terms unsettled and called for an immediate 60-day negotiating window to hash them out.

Vice President JD Vance had been scheduled to fly to Bürgenstock Resort Lake Lucerne, about an hour outside of Zurich, for a meeting on Friday that was originally meant to be a signing ceremony. He abruptly canceled his trip late Thursday night, in Washington.

The Swiss foreign affairs office confirmed on Friday morning that the meeting was off. “Switzerland remains ready to facilitate these talks,” a spokesman wrote in a news release. “The relevant preparatory work at Bürgenstock is continuing. No further information can be provided at present.”

Mr. Vance’s team had said something similar, in a release from a White House spokesman.

“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 spokesman said. “But the logistics of these negotiations have never been simple or predictable.”