The leaders of Germany and France ended more than five hours of talks with Russian President Vladimir Putin in Moscow, which Kremlin spokesman Dmitry Peskov called “constructive, informative and substantive”. The talks, however, ended without any word of an agreement to end the conflict in Ukraine.

Peskov said the leaders had agreed to continue working toward a possible joint document on implementing a cease-fire agreement signed in the Belarusian capital, Minsk, in September.

He said the document would include proposals from Putin and Ukrainian President Petro Poroshenko, and that Putin, Merkel, Hollande, and Poroshenko would hold discussions by phone on February 8.

The United States suggested it saw little sign of a shift in the conduct of the Kremlin, which Western governments are calling on to abandon support for separatists in eastern Ukraine.

"I'm not going to say it's a positive sign that they're listening," State Department spokeswoman Marie Harf said of Russia. "They've been listening. They just haven't been acting."

Harf said that "the problem isn't that there aren't enough diplomatic possibilities, it is that Russia hasn't taken any of them and hasn't lived up to its commitments."

The separatists have seized control of hundreds of square kilometers of land since the September deal and have made gains in the past month, as fighting has escalation.

Hundreds of civilians have been killed since the New Year and many others driven from their homes in midwinter, particularly around Debaltseve, the site of persistent attacks on a government-held pocket straddling a key road junction between the separatist-controlled provincial capitals of Donetsk and Luhansk.