Switzerland, June 22 -- The first round of crucial negotiations between Iran and the United States encountered an early setback on Sunday after Iranian officials declined to participate in a planned photo opportunity with their American counterparts and later walked out of the venue following remarks by US President Donald Trump threatening military action against Tehran.

The talks, being held at the Burgenstock resort in Switzerland, marked the opening session of discussions involving Iran, the United States, Pakistan and Qatar under the recently signed Islamabad Memorandum of Understanding (MoU).

According to Iran's Tasnim News Agency, organisers and members of the US delegation had arranged a handshake and joint photo session between...