German Chancellor Angela Merkel and French President Emmanuel Macron said in a joint statement in Berlin on Friday that they welcome a ceasefire agreement in eastern Ukraine.
The truce was reached by the trilateral contact group on 27 December.
The approach of the New Year and Orthodox Christmas holidays should provide an opportunity for the parties to the conflict to focus on the needs of the civilian population, who have suffered for too long, the two leaders said.
They also demanded that Russia release the Ukrainian sailors who were detained last month, along with two gunboats and a tugboat.
Moscow accused the 24 sailors of illegally crossing the Russian border in trying to enter the Kerch Strait, connecting the Black Sea with the Sea of Azov, and also of violating navigational procedures.