Kremlin spokesperson Dmitry Peskov said on Monday that preparations are underway for President Recep Tayyip Erdoğan’s upcoming visit to Sochi, Russia.

“It will be the most comprehensive agenda since bilateral relations started. These relations are multifaceted and the leaders have always something to talk about within this scope,” he told journalists.

Peskov said that Turkey and Russia would discuss Syria as well as other regional issues.

Turkey has backed opposition groups who sought to topple Bashar Assad regime, while Russia has helped shore up Assad after a decade of conflict.

Both sides have complained about violations of a truce they agreed on 18 months ago in the northwestern Idlib region, the last opposition bastion left in Syria, where Ankara says two Turkish troops were killed in an attack on Saturday.

The March 2020 agreement followed weeks of fighting that brought Turkey and Russia close to conflict and displaced nearly a million people.

Despite backing opposing sides in both the Syrian and Libyan conflicts, Turkey and Russia have forged close cooperation in the defense, energy and tourism sectors.

NATO member Turkey has bought Russian S-400 air defenses, leading to United States sanctions on Turkish defense industries, and has been in talks with Russia over possibly buying a second batch.

Ankara and Moscow were rivals in Nagorno-Karabakh during fighting between Azerbaijani and Armenian forces last year. While Russia brokered a cease-fire between Turkey-backed Azerbaijan and Armenia, it is working with Ankara to monitor it.

Turkey also angered Russia earlier this year when it sold Turkish drones to Ukraine amid tensions over the Donbass region, and later to Poland in the first such sale to a NATO member.