The Ukrainian leader repeated a few of Kiev’s central demands, which underscored the gulf between its position and that of Moscow. Ukraine endorsed decentralization but not federalization, he said, noting that the separatist regions could be granted rights similar to those in autonomous communities in Russia.

In Moscow, before he flew to Minsk, Mr. Lavrov took exception to certain Ukrainian positions, suggesting that a truce, the withdrawal of heavy weaponry and the beginning of a political process, as well as the restoration of economic ties between Kiev and the separatist regions, were far more important than control over the border.

Ms. Merkel has emphasized repeatedly that she regards the chances of success in the talks as slim, even after she and Mr. Hollande met with Mr. Putin in Moscow and with Mr. Poroshenko in Kiev on Friday. But she said the effort would continue given the daily rise in the civilian death toll from the conflict, which the United Nations has estimated at more than 5,400 since last spring.

In Germany, Norbert Röttgen, the chairman of the foreign affairs committee in Germany’s Parliament, said the talks would either come to naught or produce a retread of the original Minsk cease-fire agreement in September that might only cement the fact that the first version failed.

”I think there will either be nothing, because Putin unfortunately tactically has the upper hand in the short term,” he said, adding that Mr. Poroshenko had limited room to maneuver

“Or there will be a new cease-fire, a second Minsk, which would include a significant shift of the demarcation line to the West,” Mr. Röttgen said. “The violation of Minsk one would then be honored in Minsk two, and whether Putin would then keep to Minsk two, there are considerable doubts.”