Iran's Foreign Minister Ali Akbar Salehi got in on the Syria's "red line" rhetoric on Tuesday.
Salehi said the use of chemical weapons by anyone in Syria marks Iran's red line, though the minister did not say what actions (if any) his country would take if a poison gas attack were confirmed.
"We have always emphasized that the use of chemical weapons on the part of anyone is our red line," Reuters quoted Salehi saying via 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 added.
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Salehi then backed the claim by President Bashar al-Assad's regime - Iran's political and military ally - that rebels 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."
Last week, the White House said they believed with "varying degrees of confidence that the Syrian regime has used chemical weapons on a small scale in Syria, specifically the chemical agent sarin." Bashar's government rejected the assertion, saying Western accusations "do not have any credibility."
Also Tuesday, UN General Secretary Ban Ki-moon called on the Syrian government to allow its investigators access to alleged areas of chemical arms use.
“A credible and comprehensive inquiry requires full access to the sites where chemical weapons are alleged to have been used. I again urge the Syrian authorities to allow the investigation to proceed without delay and without any conditions,” Ban told reporters.
“This is a crucial moment in our efforts to get the team on the ground to carry out its important task,” he added.