Iran said it is suspending nuclear talks with the United States after President Donald Trump threatened to strike the country again if it did not rein in Hezbollah in Lebanon, the semi-official Fars news agency reported on Sunday. Fars cited an anonymous source as saying the talks, being held at the Swiss resort of Bürgenstock, were now in a state of "uncertainty."The development marks a sharp reversal from what had been a promising diplomatic opening. The Bürgenstock meetings were the first high-level contact between American and Iranian representatives in recent months, with US Vice President JD Vance and Iranian Foreign Minister Abbas Araghchi both in attendance. Qatar and Pakistan were also part of the talks, reflecting the multilateral framework Washington had assembled to bring Tehran back to the table.As the meetings got under way, however, Trump posted on social media that he would strike Iran again if it does not "immediately stop their highly paid PROXIES in Lebanon from causing trouble" — a reference to Hezbollah, the Iran-backed militant group that has long been a flashpoint in US-Iran tensions.Tehran has consistently maintained that its support for regional groups is non-negotiable, and Trump's public ultimatum appears to have given Iranian officials grounds to walk back from the table.The breakdown comes weeks after US strikes on Iranian nuclear facilities briefly raised fears of a wider conflict before a ceasefire took hold. Diplomatic back-channels had since opened up, with Oman and Qatar playing key mediating roles in bringing both sides to Switzerland.It is not immediately clear whether the talks have been formally ended or whether a return to the table remains possible. Fars said the situation was fluid.(With inputs from Bloomberg)