German Chancellor Angela Merkel told Russian President Vladimir Putin on the phone on Saturday that a four-way summit to discuss the situation in eastern Ukraine would not take place until there was real progress on the Minsk peace plan.
German government spokesman Steffen Seibert said in a statement after the phone call that Merkel welcomed Russian efforts to find a solution to the crisis.
However the chancellor told Putin that a summit by leaders from France, Germany, Russia and Ukraine in Kazakhstan's capital Astana or another city could not be confirmed at this stage, he added.
Ukrainian President Petro Poroshenko has invited the leaders of Russia, France and Germany to talks in Astana on Jan. 15 in an attempt to restore peace.
But Germany and France have already raised doubts on whether such a four-way summit can take place without further progress on the Minsk peace plan which was agreed on in September.
The foreign ministers of France, Germany, Russia and Ukraine will meet in Berlin on Monday to discuss the situation in eastern Ukraine and the implementation of the 12-point protocol.
Merkel's spokesman said the chancellor told Putin that all sides needed to make their contribution to implement the peace plan. "That includes that Russia uses its influence on the separatists in order to reach consensual solutions," he said.
In a separate phone call, Merkel discussed the situation in Ukraine also with Poroshenko, the spokesman said.
A four-way summit would only make sense if there was a substantial improvement on important points like a ceasefire and a demarcation line between the Ukraine-Russia border, Merkel told Poroshenko, according to the statement.
More than 4,700 people have been killed in fighting between Kiev's forces and pro-Russian rebels in eastern Ukraine since last April. The conflict has provoked the worst crisis in relations between Russia and the West since the Cold War.