ANKARA, Turkey (AP) — Russian President Vladimir Putin is traveling to Turkey for talks with President Recep Tayyip Erdogan on developments in Iraq and Syria, and Turkey's decision to purchase a Russian-made missile defense system.

Putin's visit on Thursday comes as Turkey and Russia are deepening ties in a turnaround for the two nations, which have backed opposing sides in Syria and nearly came to blows over Turkey's downing of a Russian plane in 2015.

Russia and Turkey, together with Iran, are now working on setting up de-escalation zones in Syria that have helped reduce fighting. On Iraq, Turkey has strongly opposed an Iraqi Kurdish referendum on independence which Russia neither supported nor condemned.

Some of Turkey's NATO allies have expressed concern over Turkey's decision to purchase the Russia's S-400 missile defense system.