Ways to halt the war in Ukraine and the possible launch of a new conflict in Syria are expected to dominate talks on Friday between Russian President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan.
The Turkish leader was riding high from the diplomatic success of helping orchestrate the resumption of Ukrainian grain shipments across the Black Sea when he took most of his top ministers to Sochi for his second talks with Putin in 17 days.
But there are tensions. Putin told Erdogan in Tehran last month that Russia remains opposed to any new offensive that Turkey might be planning against Kurdish militants in northern Syria.
Analysts believe these strains form part of the "competitive cooperation" that has defined the two leaders' relationship over the past 20 years.