Abbas Araghchi travelled to Geneva on Sunday to take part in renewed nuclear talks with the United States later this week.
Iran’s Foreign Ministry said he departed Tehran with a diplomatic and technical delegation for a second round of negotiations.
The ministry confirmed that indirect Iran–US talks will be held on Tuesday, with mediation by Oman.
During his visit, Araghchi is expected to meet Swiss and Omani officials, as well as Rafael Grossi.
Negotiations between Tehran and Washington resumed in Muscat on February 6 after months of stalled diplomacy and rising regional tensions.
Earlier talks collapsed last year when Israel launched a bombing campaign against Iran, sparking a brief but intense 12-day conflict.
Questions remain over Iran’s stockpile of more than 400 kilogrammes of uranium enriched to 60% purity.
Inspectors from the International Atomic Energy Agency last verified the material in June, before hostilities escalated.
Israeli Prime Minister Benjamin Netanyahu has insisted that any deal must fully dismantle Iran’s enrichment capability.
Speaking in Jerusalem, he called for the removal of equipment and infrastructure used in uranium enrichment.
Iran has signalled it may show flexibility, but only if US sanctions that are straining its economy are lifted.
Deputy Foreign Minister Majid Takht-Ravanchi told the BBC that genuine steps from Washington could pave the way for an agreement.
The talks are taking place against a backdrop of heightened US military pressure, including the deployment of an aircraft carrier group to the region.
Washington’s warning came after Iran’s deadly crackdown on anti-government protests last month.
Araghchi previously led negotiations in Muscat with US envoy Steve Witkoff and presidential adviser Jared Kushner.
Switzerland, which has represented US interests in Iran since diplomatic ties were severed following the 1980 hostage crisis, continues to act as an intermediary.
Iranian officials say any future agreement must deliver swift economic benefits, particularly in aviation, mining, oil and gas.