The 'contact group' of Egypt, Iran, Turkey and Saudi Arabia was assembled at Egypt's initiative, but an Egyptian official said the Saudi foreign minister was staying away for health reasons, without saying why no one else was coming in his place.
Turkish Foreign Minister Ahmet Davutoğlu also said Saudi Arabia, which attended a preparatory meeting last week, would be absent on Monday, but that it would join in future meetings. There was no immediate Saudi comment.
Saudi Foreign Minister Prince Saud al-Faisal had an operation last month, keeping him away from official business, but he has been represented at international meetings by Deputy Foreign Minister Prince Abdulaziz bin Abdullah.
Diplomats and Western officials have been sceptical that the group can reach any tangible agreement, particularly when it includes both Sunni Saudi Arabia and Shi'ite Iran, who have tussled for influence in sectarian conflicts across the Middle East.
Turkey, Saudi Arabia and Egypt have all demanded that Syrian President Bashar al-Assad step down, while Iran is his main ally and accuses states including Saudi Arabia and Turkey of helping the rebels who are fighting to topple him.
Against that backdrop, some analysts said Egypt may itself not have expected much from the group and that Egyptian President Mohamed Mursi's main aim may have been to put Cairo back on the map as a regional power broker.
One ambassador to the Arab League said it was "not possible for regional states to succeed in solving this (Syrian) file in light of the differences between Russia and China on one side and America and the West on the other".
China and Russia have vetoed Western- and Arab-backed U.N. Security Council resolutions intended to put pressure on Assad.
The UN-Arab League mediator on Syria, Lakhdar Brahimi, in Cairo after making his first trip to Damascus in his new post, was due to join the foreign ministers' meeting later on Monday.
Brahimi met Arab League chief Nabil Elaraby, but made no public statement.
Davutoğlu said Brahimi should have a different mandate from Kofi Annan, the former U.N. secretary-general who quit as Syria envoy complaining about the impasse at the Security Council.
"He must not allow Assad to buy more time with this type of mission," Davutoğlu said. "Assad misused Kofi Annan's mission to increase pressure on people. Brahimi shouldn't give Assad this chance."
A diplomatic source told the daily Al-Ahram that Egypt would seek agreement at Monday's meeting on a call for an immediate halt to the violence, a rejection of any foreign military intervention, and an endorsement of Syrian unity.
The meeting also aimed to help to bring together Syria's myriad groups and sects to achieve its people's "aspirations for democracy, freedom and dignity", the paper said.