Iranian Foreign Minister Abbas Araghchi has left Tehran for Geneva for a third round of nuclear talks with the United States.
The two countries have already held two rounds of Oman-mediated talks to replace a 2015 deal derailed by US President Donald Trump during his first term in power.
Trump has pursued his "maximum pressure" policy, deploying naval and aerial power to the region and issuing threats of attacks.
Trump has called for Iran to dismantle its nuclear industry altogether. Tehran has rejected the demand, insisting that it has the right to use nuclear technology for peaceful purposes.
Iran has vowed to give a crushing response to any military attack, even limited ones.
Iran has conducted several rounds of military drills in recent days, including in the country's south and near the strategic Strait of Hormuz in the Persian Gulf.
The two sides held five rounds of talks last year, which collapsed after the United States and the Israeli regime launched a 12-day war that killed more than 1,060 Iranians and injured some 6,000 others.
The US and Israel, Iranian authorities say, also armed and encouraged terrorists who committed Daesh-style crimes in Iran last month that resulted in the martyrdom of 2,427 civilians and police forces.