The leaders of France and Germany have spoken for more than two hours by telephone with presidents of Russia and Ukraine, seeking progress before a fragile ceasefire between Kiev and pro-Kremlin separatists expires.
German Chancellor Angela Merkel and French President Francois Hollande joined Vladimir Putin on Sunday in asking Ukraine's President Petro Poroshenko to extend the truce in the country's troubled east, the Kremlin said in a statement issued after a four-way phone conference.
However, fighting flared on Sunday between Ukrainian forces and separatists around the eastern flashpoint city of Slaviansk despite the truce.
The talks came in the run-up to a Monday deadline that European Union leaders set for Russia and the separatists to take steps to ease the violence, warning that they were ready "at any time" to impose further punitive measures.
The European leaders encouraged the Ukrainian and Russian presidents to work on meeting the EU conditions, Hollande's office said in a statement.
The EU's demands included the return of three border checkpoints to Ukrainian control, verification of the ceasefire by monitors from the Organisation for Security and Cooperation in Europe, free hostages and talks to put Poroshenko's peace plan in place.
Tensions remain high
The call was the latest in a series of discussions the four leaders have held in recent weeks in an effort to stop the fighting that has killed more than 400 people since April. A ceasefire in place since June 20 has been shaky, with each side accusing the other of numerous violations.
A statement released by Poroshenko's office said he underlined Ukraine's willingness to maintain a ceasefire at least until Monday evening, but expressed concern about the situation.
The four agreed to speak again on Monday according to the new Ukrainian president's office.
In another indication that tensions remain high, several hundred Ukrainian soldiers and activists gathered outside the presidential administration in Kiev on Sunday to demand that Poroshenko lift the ceasefire and allow them to resume their fight.
A presidential administration official, Henadiy Zubko, promised to pass on their demands to the president, but told them that the ceasefire order would remain in effect until 1900GMT on Monday .
Another EU condition was fulfilled late on Saturday, when pro-Russia separatists released a second team of four OSCE observers who had been held captive in eastern Ukraine since the end of May. The first team of four was freed last week.