Turkish chief of staff Hulusi Akar met with his Russian and Iranian counterparts in Russia's Sochi late Tuesday ahead of a trilateral summit scheduled on Wednesday between the presidents of Iran, Russia and Turkey.

According to sources, Iran's Major General Mohammad Bagheri, Russia's Valery Gerasimov and Chief of Staff Akar discussed areas of de-conflict zones in Syria.

Akar headed to Russia's Black Sea resort of Sochi to attend a trilateral meeting earlier in the same day.

Turkey and Russia, together with Iran, are the guarantor countries that brokered a cease-fire in Syria in December 2016, leading to the Astana talks, which ran parallel to the U.N.-backed discussions in Geneva to find a political solution to the six-year war.

Russian President Vladimir Putin had a meeting with Syria's Bashar Assad also on the same day and discussed the political settlement process in the war-torn country.

On Wednesday, President Recep Tayyip Erdoğan will also travel to Sochi to attend a trilateral summit on Syria.

The leaders will discuss the progress on reducing violence in Syria and de-escalation zones, which were established after the Astana talks.

They will also handle the delivery of humanitarian aid to Syria and possible contributions to the Geneva process toward a political solution in the country under U.N. Security Council Resolution 2254.

The resolution adopted in December 2015 endorsed a road map for the peace process in Syria.

Erdoğan was in Russia on Nov. 13 to discuss the Astana process and his visit Wednesday will mark the sixth time he meets his Russian counterpart.

On May 4, Russia, Turkey and Iran signed a deal in the Kazakh capital Astana to establish de-escalation zones in Syria.

The May 4 de-escalation zone agreement envisages the halt of hostilities between Assad regime forces and moderate opposition groups within the zones as well as the creation of conditions for humanitarian access, medical assistance, the return of displaced civilians to their homes and the restoration of damaged infrastructure. The guarantor states previously agreed to take all measures necessary to continue fighting Daesh, al-Nusra and other terrorist groups both within and beyond the de-escalation zones.