Iran has warned the US not to cross the “red line” on Syria, saying it would have “severe consequences”, according to the Fars news agency.
Iran’s comments have come after the UK and the US have threatened a “serious response” if it emerges Syria used chemical weapons last week.
Prime Minister David Cameron and President Barack Obama spoke on the telephone for 40 minutes on Saturday.
Both were “gravely concerned” by the “increasing signs that this was a significant chemical weapons attack carried out by the Syrian regime“, Mr Cameron’s office said in a statement.
The Syrian government has denied involvement and blamed rebel fighters.
On Sunday, the White House said there was “very little doubt” that Assad’s regime had used chemical weapons against civilians.
“America knows the limitation of the red line of the Syrian front and any crossing of Syria’s red line will have severe consequences for the White House,” said Massoud Jazayeri, deputy chief of staff of Iran’s armed forces, reacting to statements by Western officials regarding the possibility of military intervention in Syria.
Earlier, Iranian Press TV reported that Damascus had told Tehran it would allow inspectors to visit the site of the alleged chemical attack.
A Downing Street spokesperson stressed that any significant use of chemical weapons would merit a “serious response”.
US Defence Secretary Chuck Hagel said the American military is ready to exercise “options” on Syria should force be called for, but he declined to say what that action might be.
He is under mounting pressure to act over the alleged use of chemical weapons, which humanitarian organisation Doctors Without Borders said had killed 355 people due to “neurotoxic” symptoms.
The group says it has treated more than 3,500 people showing symptoms of exposure to a “neurotoxic” agent.