US Vice President JD Vance has delayed his trip to Switzerland as logistical details for expected technical talks with Iran remain unresolved, said the White House.

"As of now, the US vice president is not departing tonight," a spokesperson said on Thursday.

Vance had been expected to travel to Switzerland as part of efforts to advance discussions linked to Iran.

"As the vice president said at his press conference, the plans for the upcoming technical talks have not been finalised, and the US 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.

The US looks forward to beginning technical talks "as soon as possible," the spokesperson added.

Earlier on Thursday, Vance told reporters that he plans to go to Switzerland, and technical talks with Iran might start "this weekend."

"I plan to go to Switzerland. Exactly when, you know, we thought we, I think these technical negotiations are going to start sometime this weekend. That's still the plan. But that could change because it's not an easy country, Iran, to get out of. And so, we're trying to figure out exactly when that's going to happen. I suspect this weekend, but I'm not sure," he said.

In Iran, the Tasnim agency said "nothing has been confirmed" about the Iranian delegation's trip to Switzerland.

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'Different view'

Mojtaba Khamenei, who became supreme leader after his father, Ali Khamenei, was assassinated in a US-Israeli air strike on the first day of the war on February 28, said in a written statement that he had approved the deal despite having a "different view", without elaborating.

"But I issued my permission due to the commitment" made by officials, including President Masoud Pezheshkian, to "protect the rights of the Iranian nation".

"Face-to-face negotiations" with the US will be held in the future, but that does not "mean accepting the enemy's point of view", he added.

On Friday, Iran's chief negotiator Mohammad Bagher Ghalibaf, warned against any breach of the agreement on X: "In case of misconduct, breach of treaty and excess of the other side, We have no doubt that decisive respond will be given to the enemy."

Before Vance delayed his trip, Pakistani Prime Minister Shehbaz Sharif postponed a planned visit to Switzerland, where Islamabad officials had originally planned to host a ceremonial signing ceremony for the agreement.

That visit was postponed because the agreement had already been signed by both Iran and the US, said two senior officials who spoke on condition of anonymity because of the sensitivity of the matter.