The United States informed Iran in advance of its intention to strike Islamic State (IS) militants in Syria and assured Tehran that it would not target the forces of Syrian President Bashar al-Assad, an Iranian official told Reuters.
The communication, confirmed in part by a senior US State Department official, may signal the two countries are inching toward a level of contacts rarely seen before.
Speaking on condition of anonymity, the Iranian official said Tehran had voiced concern for Assad, one of its closest regional allies.
"Iran was concerned about Assad's position and his government being weakened in case of any action against IS in Syria and brought this issue up in meetings with Americans," the Iranian official said.
"This issue was first discussed in Geneva and then was discussed thoroughly in New York where Iran was assured that Assad and his government will not be targeted in case of any military action against Daesh (Islamic State) in Syria."
The official said Iran was informed separately in advance of the airstrikes launched by Washington and Arab allies against Islamic State positions in Syria for the first time.
Asked about the assurance that Syrian government forces would not be targeted, the senior US State Department official told Reuters, "We communicated our intentions, but not specific timing or targets, to the Iranians. As we've said, we won't be coordinating military action with Iran. And of course we won't be sharing intelligence with Iran either."
Both Iran and the United States acknowledge having an interest in defeating Islamic State.
Speaking to senior editors in New York on Tuesday, President Hassan Rouhani raised questions about the legality of the airstrikes by the United States and Arab allies.
"The bombardment must have a certain framework that is needed to take place in a third country." He said without a UN mandate or a request from the government of the affected country, military interventions "don't have any legal standing."
Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei has ruled out cooperating with the United States to tackle the IS extremist militant group.
