JEDDAH, Saudi Arabia — Leaders of Muslim countries, including Iran's pro-Syrian President Mahmoud Ahmadinejad, will gather Tuesday for an extraordinary summit called by Saudi King Abdullah who is pushing to mobilize support for the Syrian rebellion.

"The Syrian issue will be a top priority" in the summit taking place in the Muslim holy city of Mecca, according to Ekmeleddin Ihsanoglu, the secretary general of the Organization of Islamic Cooperation (OIC).

War-ravaged Syria will not be represented in the summit, the head of the Jeddah-based 57-member organization told AFP, adding that a preparatory meeting of OIC foreign ministers on Monday announced "the suspension of Syria's membership as recommended by member states."

The two-day summit convenes as fighting rages over Syria's northern city of Aleppo between rebels and troops loyal to President Bashar al-Assad, 17 months into a countrywide conflict that has cost more than 21,000 lives, according to monitors.

But the Saudi effort to reach agreement over a solution to the deadly crisis is not expected to be smooth sailing, as Iran's firebrand leader is a staunch ally of Damascus, while Tehran has repeatedly accused Saudi Arabia, as well as Qatar and Turkey, of arming and financing the rebels.

"The world today is in a very sensitive situation," Ahmadinejad told reporters on Monday just before leaving Tehran for Saudi Arabia, according to the Fars news agency. "Different groups are at work and the enemies are actively pursuing their aims and a great deal of energy is being spent by Islamic governments and groups on arguing with and confronting each other.

"I hope that the summit will focus on increasing unity and lowering antagonism," he said.

Tehran last week held its own 29-nation conference on Syria attended mostly by ambassadors from like-minded countries, notably Russia and China, two other strong allies of Damascus. Saudi Arabia shunned the meeting.

U.S. officials and the Syrian opposition claim Iran has sent military aid, including advisors and telecoms surveillance equipment, to Damascus. Tehran denies it has any active forces in Syria.

"Saudi Arabia has called for the meeting after exhausting all possible means to solve the Syrian crisis," said the head of the Gulf Research Center, Abdulaziz Sager.

The Saudi analyst said the summit "should adopt a resolution for a peaceful transfer of power in Syria, including the departure of president Assad and the formation of a national union government."

Meanwhile, the head of the Syrian opposition in exile called on the summit to adopt a "firm position to end the daily killing and force the regime to quit."

Abdel Basset Sayda, who heads the opposition Syrian National Council, told AFP that the rebels need the imposition of "two no-fly zones, one in the north, close to the Turkish border, and another in the south, close to the border with Jordan," in addition to "safe places for refugees and humanitarian corridors."

The Syrian opposition was not invited to attend the Mecca summit.

On Sunday, ministers of the six-nation Gulf Cooperation Council met in Jeddah to "coordinate" their position ahead of Tuesday's summit, said the GCC secretary general Abdullatif al-Zayani.

But a Sunday meeting for Arab foreign ministers to consider their next moves after the resignation of the UN-Arab League envoy to Syria Kofi Annan this month was postponed without giving a new date.