Flags of Switzerland, United States, Iran, Qatar, Pakistan and local Swiss canton of Nidwalden are photographed at the Burgenstock luxury hotel complex overlooking Lake Lucerne, Switzerland. AFP
Before boarding his flight to Europe, Vance told reporters he hoped to "make progress on the nuclear issue, make progress on the Lebanon ceasefire issue. Those are the two big things that I think we're going to be focused on".
Follow-up talks had been planned in Switzerland on Friday but were postponed at the last minute after Israel launched deadly strikes in Lebanon.
Washington announced a renewed ceasefire there later Friday -- a condition of its preliminary agreement with Iran -- but Israeli forces resumed airstrikes and clashed again with Hezbollah resistance fighters on Saturday, effectively breaching the ceasefire.
Lebanese state media reported Israeli air raids on around 20 locations, with authorities said more than 30 people were killed. The overall death toll from Israeli attacks in Lebanon had surpassed 4,000, the health ministry said.
Citing a US "breach of contract" and "the Zionist regime's continuous and relentless violation of the ceasefire in southern Lebanon", Iran's central military command said "the Strait of Hormuz will be closed to vessel traffic".
Tehran had agreed to reopen it under the preliminary accord signed by US President Donald Trump and his Iranian counterpart Masoud Pezeshkian, and shipping traffic had begun to recover.
US Central Command said after Iran's announcement that safe passage through the international waterway had "remained intact" and that US forces were "present and vigilant".
Trump later warned that Washington could impose its own tolls on Hormuz if negotiators failed to complete the deal.
There would be no tolls "unless they are imposed by and for the United States of America", Trump wrote on Truth Social.
Switzerland push
An Iranian delegation arrived in Switzerland late Saturday, state media and the Swiss foreign ministry said.
Iran's official broadcaster said it included parliamentary speaker Mohammad Bagher Ghalibaf and Foreign Minister Abbas Araghchi.
Foreign ministry spokesman Esmaeil Baqaei said the delegation would "demand implementation of the other party's commitments" under the deal.
"Otherwise, the entire understanding will be in trouble," he said, according to official news agency IRNA.
Vance arrived at the Emmen Air Base in Switzerland on Sunday morning, having earlier said he could only stay "a day or two".
US negotiators Jared Kushner and Steve Witkoff were already there handling "some of the technical elements" and had reported that "things are going well", Vance said in an interview with Fox News earlier Saturday.
Pakistan, which has been helping to mediate, said Sunday that Prime Minister Shehbaz Sharif and army chief Asim Munir had left for Switzerland to take part in high-level talks involving US and Iranian representatives and other mediators from Qatar.
The talks are meant to open a two-month negotiation period on issues left unresolved by the initial accord, notably Iran's nuclear programme.
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