Iran and the U.S. are trying to resolve their decades-long standoff over Tehran's atomic aims under the shadow of Trump's threat to unleash military action if diplomacy fails.

US and Iranian delegations will gather in Rome Saturday for a second round of high-level talks on Tehran’s nuclear program amid tempered optimism about a diplomatic way forward.

Iran and the United States began a second round of negotiations Saturday over Tehran's rapidly advancing nuclear program in Rome, U.S. and Iranian officials said. The U.S. official spoke on condition of anonymity to discuss the closed-door negotiations at the Omani Embassy in Rome’s Camilluccia neighborhood.