Russia, Turkey and Iran, which helped broker the withdrawal of civilians and militants from the Syrian city of Aleppo, have agreed to hold talks on Syria in Kazakhstan next month.
Erdogan said today the meeting of foreign ministers should include Saudi Arabia and Qatar, saying they had "shown goodwill and given support" to Syria.
Turkey, Saudi Arabia and Qatar are the main backers of rebels seeking to topple Syrian President Bashar Assad, who is closely allied with Moscow and Tehran.