Russian President Vladimir Putin will travel to Ankara Sept. 28 to hold talks on regional developments with President Recep Tayyip Erdoğan, Kremlin said Thursday.

According to Kremlin Spokesperson Dmitriy Peskov, preparations for Putin's visit to the Turkish capital were already underway.

The meeting is expected to cover a wide range of topics, including Syria, Kurdistan Regional Government (KRG) independence referendum and Turkey's purchase of Russian S-400 missile defense systems.

Speaking at the Bloomberg Global Business Forum in New York on Wednesday, Erdoğan said he would discuss the situation in Syria with Putin over the phone next Monday and meet with him in person next Thursday, but did not provide any details.

The two presidents are expected to touch upon the topic of a de-escalation zones in northwestern province of Idlib. Last week in Astana, Turkey, Russia and Iran agreed on deploying hundreds of observers around the province to check de-escalation efforts.

Earlier on Sept. 10, Erdoğan said that Turkey was determined to procure the S-400 air defense system, dismissing claims that Ankara might give up on the deal because of strong opposition from NATO.

He also confirmed that a primary deposit for the purchase has already been transferred to Moscow.

Besides the quick recovery of economic relations, following the November 2015 jet-downing crisis, Moscow and Ankara played key roles in stopping the bloodshed in Syria by agreeing and overseeing the evacuation of Aleppo late last December.

Along with Iran, the two countries also took the initiative to bring the Assad regime and the Syrian opposition together in Astana to sustain a ceasefire agreement and negotiate a political transition in the country.

Erdoğan and Putin agreed to lift nearly all sanctions imposed on Turkish services, products, textiles and the construction sector during their last meeting in Sochi on May 3.