Iran said the move could set a dangerous precedent.
Iran criticised the Arab League for allowing an opposition leader to fill Syria’s vacant seat at the organisation’s annual summit and described it as “dangerous behaviour”, Iranian media reported.
With Syrian membership of the Arab League suspended in November 2011, the seat at Tuesday’s summit was filled by Moaz Alkhatib, the leading figure among Syria’s opposition coalition that is battling to overthrow President Bashar al-Assad.
Shiite Iran has given crucial backing to Assad since the protests erupted in Syria in 2011.
Tehran regards him as key in the axis of resistance against Israel and a bulwark against what it says are extremist Sunni groups operating in Syria.
“Assigning Syria’s seat in the Arab League to those who don’t have the backing of the people establishes a pattern of dangerous behaviour for the Arab world that can set a new precedent for other members of the Arab League in the future,” said deputy foreign minister, Hossein Amir Abdullahian.
“These actions will bring an end to the organisation’s role in the region,” he said.
At the summit, Moaz Alkhatib put a request to U.S. Secretary of State, John Kerry, demanding that American forces help in defending rebel-controlled northern parts of Syria with Patriot surface-to-air missiles based in Turkey.
NATO swiftly rebuffed the idea.
The summit also endorsed the provision of military aid to Syrian rebels.
A communiqué affirmed that member states had a right to offer assistance “including military, to support the steadfastness of the Syrian people and the Free Army”.
Iran has proposed a six-point plan for Syria and emphasised the importance of elections and reforms, but does not accept the removal of Assad.
It said a solution to the crisis cannot be imposed from outside the country.