STORY: The three countries are working together to try to reduce the violence in Syria despite supporting opposing sides in the war.
Russia and Iran are Syrian President Bashar al-Assad’s strongest backers, while Turkey supports anti-Assad insurgents.
Turkey's President Tayyip Erdogan has threatened to launch another operation in Northern Syria, which Tehran and Moscow oppose.
In Tehran, Putin and Erdogan will meet to discuss a deal aimed at resuming Ukraine's Black Sea grain exports.
The prospect of an emerging U.S.-backed Arab-Israeli bloc that could tilt the Middle East balance of power further away from Iran has accelerated its clerical rulers' efforts to strengthen strategic ties with the Kremlin.