In calling chemical weapons use a “red line” for Iran, Foreign Minister Ali Akbar Salehi did not indicate what action Tehran – one of Assad’s staunchest political and military allies – might take in the case that a poison gas attack by either side in the conflict were to be proven.

“We have always emphasized that the use of chemical weapons on the part of anyone is our red line,” Salehi said, according to the ISNA news agency. “Iran is opposed to the use of any kind of weapon of mass destruction, and not just their use but their production, accumulation, and use.”

Salehi also reiterated calls for the United Nations to investigate assertions by the Syrian government that Syrian insurgents had used chemical weapons.

“On Syria,” he said, “we have also requested that in accordance with the Syrian government, which emphasizes that the opposition has used these weapons, the United Nations…identify the main culprit in this regard, which is the opposition.”