BERLIN — Germany's foreign minister is hosting his counterparts from Russia, Ukraine and France to try to calm the Ukrainian crisis and perhaps clear the way for a summit of the countries' leaders.

The Berlin meeting on Monday evening follows a flurry of diplomacy including a brief weekend encounter in Paris between the German, French and Ukrainian leaders.

German Chancellor Angela Merkel also has spoken by phone with Russian President Vladimir Putin and met the president of Kazakhstan, the possible host of a four-way summit on Ukraine.

Merkel and Foreign Minister Frank-Walter Steinmeier are pushing for progress on implementing a much-violated peace deal that was drawn up in September. Berlin says a substantial narrowing of differences between Ukraine and Russia is needed for a summit to take place.

The Kremlin also said Monday that prospects for the meeting depend on the outcome of the talks in Berlin.

The two sides have remained wide apart on major conditions of a peace deal. Ukraine and the rebels have failed to agree on a line of division, and fighting in eastern Ukraine between the government and pro-Russian rebels has escalated in recent days.

Speaking in Moscow on Monday before heading for Berlin, Russian Foreign Minister Sergey Lavrov sternly warned Ukraine against trying to crush the pro-Russian rebellion by force.

He said that Russia expects the West to use its influence with Kiev to discourage it from launching another offensive, adding that "it will be a catastrophe."

The pro-Russia rebellion flared up in Ukraine's mostly Russian-speaking eastern regions following Moscow's annexation of Ukraine's Crimean Peninsula in March. More than 4,700 people have died in fighting in the east since April, according to the United Nations.

Lavrov reaffirmed that the rebel-controlled territories should remain part of Ukraine, but stressed that the government in Kiev must implement a constitutional reform that would expand the powers of the regions.

Vladimir Isachenkov in Moscow contributed to this report.