German Chancellor Angela Merkel told the leaders of Russia and Ukraine that she's not ready to take part in a four-way summit over the Ukraine conflict unless there's a chance of real progress.

After talking with Presidents Vladimir Putin of Russia and Petro Poroshenko of Ukraine on the phone Saturday, Merkel met Sunday with Poroshenko and French President Francois Hollande at the presidential palace in Paris. The latter three leaders were in the French capital to attend a rally there paying their respects to the victims of the three days of terror in Paris that started with an attack on satirical newspaper Charlie Hebdo.

French, Ukrainian and German government officials confirmed the 15-minute-long meeting, but didn't give any details. A French government official said Russian Foreign Minister Sergey Lavrov, who was also in Paris for the rally, didn't attend the meeting.

The leaders of Germany, Russia, Ukraine and France are working on setting up a possible meeting in Astana, Kazakhstan. But Merkel's office said late Saturday that it's not yet clear whether the meeting can take place.

In talks with Russian President Vladimir Putin and Poroshenko, she stressed that for the meeting to be successful there has to be progress on implementing a much-violated peace deal that was drawn up in Minsk in September. Merkel has insisted that every point of that agreement must be fulfilled.

The foreign ministers of the four countries will meet in Berlin on Monday.