Russian, Turkish and Iranian presidents will hold separate meetings on the sidelines of a trilateral summit on Thursday in the Russian Black Sea city of Sochi, according to a Kremlin statement Monday.
The three leaders will discuss projects and coordination on the international arena, it said.
At the fourth meeting in the Astana format, Vladimir Putin, Recep Tayyip Erdogan and Hassan Rouhani will concentrate on the long-term settlement of the Syrian crisis.
The leaders first met in Sochi in 2017.
The three are guarantor countries which brokered a cease-fire in Syria in December 2016, leading to the Astana talks, which are running parallel to the Geneva talks.
By Elena Teslova in Moscow