Iranian President Hassan Rouhani, Turkish President Tayyip Erdogan and Russian President Vladimir Putin met in in Ankara on Wednesday for a three-way summit on the Syrian conflict.The leaders were determined to speed up efforts to ensure "calm on the ground" in Syria, and to protect civilians in "de-escalation areas," according to a joint statement posted on Rouhani's presidential website.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.Despite their differences Iran, Russia and Turkey are three of the major powers involved in a conflict whose course has been largely defined by foreign interventions, and their influence could increase further if the United States pulls out.Rouhani blamed the United States for backing Islamic State militants in Syria and called on all countries to respect the independence of its main Arab ally in the Middle East."Some countries, including America, support terrorist groups like Islamic State in Syria, which serve these countries' interests... Iran believes the Syrian crisis has no military solution and safeguarding independence of Syria a priority for Tehran," Rouhani told a news conference in Ankara. Rouhani also told his colleagues that the Syrian region of Afrin, captured by Turkish forces and their Syrian rebel allies, should be handed over to Syria's army, Iranian television said."The developments in Afrin can only be useful if they do not violate Syria's territorial integrity, and control of these areas should be handed over to the Syrian army," Rouhani said.Erdogan said that Syria's territorial integrity depended on maintaining distance from all terrorist organizations, a reference to US support for a Syrian Kurdish militia Ankara considers an enemy.Erodgan also said that hope for success in Syria was growing stronger.