Iran's top joint military command,Khatam al-Anbiya Central Headquarters, said on Saturday that the Strait of Hormuz would be closed to vessel traffic, citing alleged violations of a ceasefire agreement by the US and Israel and US "bad faith" and "its clear breach of its commitments" by failing to end the war, Iran's Mehr state news agency reported.
It said that the closure was the "first step" in response to what it described as breaches of commitments and warned that further measures would be taken if "aggression" continued.
Ships had begun transiting the strait after the interim US-Iran agreement was signed earlier in the week.
Israeli strikes on southern Lebanon on Saturday killed at least 16 people, including two children, hours after reports emerged of a ceasefire agreement. The persistent fighting threatened an interim agreement between the US and Iran to end the war in the Middle East.
Amid Hormuz closure, Pakistan's foreign ministry said on Saturday that follow-up technical-level talks between Iran and the US will be held in Bürgenstock, Switzerland, on June 21.
A US delegation led by Vice President JD Vance is expected to participate in upcoming talks with Iran in Switzerland, alongside Iranian representatives and mediators from Pakistan and Qatar. Vance in an interview with Fox News said on Saturday that he expects to travel to Switzerland soon for the negotiations, despite Tehran's announcement that it would close the Strait of Hormuz.
"We'll plan the talks when the principals from the Iranian government, also the Qatari and the Pakistani governments arrive. That may happen as soon as tomorrow, but these things are always a little bit in flux," Vance said.
"Jared Kushner and Steve Witkoff have been on the ground now for a few hours, dealing with some of the technical elements of this negotiation," Vance added.
US President Donald Trump and Iran President Masoud Pezeshkian signed the Memorandum of Understanding to end the over three-month war and technical aspects of the agreement were to be discussed by negotiators in Switzerland beginning Friday.
However, there was a delay due to a fresh round of firing between Israel and Lebanon.
"My understanding, talking to Jared and Steve this (Saturday) morning, is things are going well," Vance said.
"What a lot of the criticisms of the deal have really underappreciated is that the United States has all the cards. The straits are now open. The Iranian military is now destroyed. The Iranians have committed to, of course, destroying that stockpile of enriched material," Vance said.
"But we have a lot of economic pressure applied to the Iranians that we would be willing to relieve if they do what we need them to do. If they don't do that, of course, there's no skin off our back. They're still in a much weakened position," Vance said.