Talks between the US and Iran in Switzerland were abruptly called off on Friday, clouding prospects for a lasting truce as a major escalation in Lebanon sparked chaos in the Strait of Hormuz and threatened the tenuous agreement to end the war.

Switzerland’s foreign ministry told The Independent that talks at the mountaintop resort of Bürgenstock had been postponed, without further explanation. Insiders said Iran had refused to attend after Israel ramped up airstrikes in Lebanon, killing at least 47 people, according to the Lebanese health ministry.

As renewed fighting in the region threatened to derail the peace process, Israel and Hezbollah suddenly agreed to a renewed ceasefire late on Friday afternoon. But on a chaotic day in the Middle East, Israeli airstrikes could still be seen across the border more than an hour after the truce was meant to take effect.

The sudden eruption of clashes provoked Tehran to fire warning shots at ships in the Strait of Hormuz and threaten that the vital waterway “will remain closed” until Israel withdraws from Lebanon and other terms of the memorandum of understanding (MoU) are met, the FT reported.

But Iran softened its tone after the latest Israel-Hezbollah ceasefire and said plans were underway for a new meeting with the US in the coming days.

Iran’s foreign ministry also claimed that because the MoU with the US had been signed digitally earlier in the week, the meeting in Switzerland was less urgent. Spokesperson Esmaeil Baghaei insisted shipping through the Strait of Hormuz would continue.

Suspicion remained with Iran’s top negotiator, Mohammad Bagher Ghalibaf, resolute that Tehran would have no hesitation in delivering a “crushing response” in the event of “bad faith, breach of contract, and excessive demands” from the US.

“They were once slapped during the war; if they wish to tread that path again, they will receive an even harder slap,” he wrote on social media as Trump insisted Iran was already “finished”, against mounting criticism at home over his 14-point deal to end the war.

Trump rushed to defend his record on Friday after Iran’s supreme leader claimed he had forced through an agreement to end the war out of “desperation”.

“We didn’t meet out of desperation, Iran did,” the US president wrote on Truth Social. “They are FINISHED! We’ll play out the 60 days. They get no money, not ten cents!”

Despite the rhetoric, both Iran and the US were keen to avoid a return to hostilities and a senior US source said that America and Qatar had worked on the Israel-Hezbollah deal with help from Iran.

Netanyahu said Israel would remain in the buffer zone for “as long as we need to” despite the new ceasefire, which renews an existing agreement nominally in place since April. The military earlier released a new map showing an expanded zone of control in Lebanon.

Earlier in the day, Hezbollah said it had ambushed an Israeli force near the Ali al-Taher hill, destroying three Merkava tanks and targeting troops with rocket and artillery fire.

The IDF reported that four of its soldiers had been killed in an incident in Lebanon, drawing furious responses from senior Israeli officials, including hawkish national security minister Itamar Ben Gvir who wrote that “for every tear of an Israeli mother, a thousand Lebanese mothers must weep. All of Lebanon must burn!

“In the Middle East, you don’t win with measured responses and restraint – you need to go berserk. To obliterate. To crush the terror,” he said in a post on social media, several hours before the new ceasefire was announced.

Far-right finance minister Bezalel Smotrich, another lynchpin in Israel’s coalition government, concurred that it was “time to speak with fire” and “open the gates of hell”.

Trump has repeatedly urged Israel not to escalate the conflict in Lebanon, having pledged to end the war on all fronts as part of his bilateral agreement with Iran signed this week.

In comments to Axios this week, Trump restated his claim that “if it weren’t for me, Israel would not exist today”. He said his relationship with Netanyahu was “good, but we have to keep him a little bit sane”.

The US president continued to defend his interim deal to end the war with Iran, in light of growing backlash from his Republican base. He responded to the criticism saying: “Some guys that I used to respect, I don’t respect anymore. They’re hardliners.”

When pressed on why the deal as reported does not resolve all his original war objectives, the president insisted the outcome amounts to an “unconditional surrender” by Iran as well as de facto “regime change”.