The leaders of France, Germany, and Ukraine said they were "concerned" about post-ceasefire fighting in the encircled town of Debaltseve in eastern Ukraine.
A ceasefire in eastern Ukraine was negotiated last week, but the government-controlled town of Debaltseve has been hit by heavy fighting between rebels and thousands of Ukrainian troops effectively trapped there.
French President Francois Hollande's office said Hollande, German Chancellor Angela Merkel, and Ukrainian President Petro Poroshenko, who all spoke by telephone on February 16, called for observers from the Organization for Security and Cooperation in Europe (OSCE) to have "free access" for their work in eastern Ukraine.
The OSCE said on February 15 that rebels in eastern Ukraine refused to allow its monitors to reach Debaltseve after the ceasefire took effect.
The rebels have said the ceasefire does not apply to Debaltseve