The US-led air strikes on Isis targets in Syria are illegal and should have been conducted only after receiving consent from the Syrian government, Iran's President Hassan Rouhani has reportedly said.
In a meeting on the first day of the United Nations General Assembly gathering of world leaders, Mr Rouhani stressed that Iran condemns the barbaric actions committed by Isis and said Iran stands ready to help fight terrorism.
When asked for his reaction to US-led air strikes on Isis in Syria, he said: "The bombardment must have a certain framework that is needed to take place in a third country."
Without a UN mandate or a request from the government of the affected country, military interventions "don't have any legal standing", he was quoted as saying by Reuters.
Mr Rouhani said the US policy is confused because it simultaneously opposes the militants while also trying to undermine the government of Syria's President Bashar al-Assad.
MSNBC's Andrea Mitchell tweeted on Tuesday that Mr Rouhani told her the strikes were "illegal", as did The Nation's editor Katrina VandenHeuvel.
"This is clearly nebulous and ambiguous at best," he said. "This is a very confusing behavior and policy."
President Assad is a close ally of Iran, which has provided military support to his government during its civil war.
The US and Iran have been unable to work together to combat the Islamic State group, complicating efforts against militants that both Washington and Tehran see as a threat.
Iran's supreme leader, Ayatollah Ali Khamenei, who has the final say on all state matters, decisively ruled out an alliance. He said Iran had rejected an invitation by US Secretary of State John Kerry to discuss cooperation.