A pro-Russian fighter in eastern Ukraine after taking an oath of allegiance to the self-proclaimed Donetsk People's Republic.
Evgeniy Maloletka/Associated Press.
A statement posted late Saturday on the Kremlin's website was Mr. Putin's most direct call to date for a cease-fire. Moscow has previously insisted that it does not hold sufficient sway over the pro-Russian separatists to influence their position.
"The president of Russia calls on all parties to the conflict to cease hostilities and sit down at the negotiating table," the statement said.
The statement said Mr. Putin supported the declaration of a unilateral cease-fire by President Petro O. Poroshenko of Ukraine on Friday, "as well as his intent to take a number of specific measures to reach a peaceful settlement." But it said the plan would be neither "viable nor realistic" without practical steps to begin negotiating with the separatists, who have declared autonomy in two southeastern regions.
Mr. Putin also described as "unacceptable" the firing of Ukrainian shells into a Russian border post on Friday night, soon after the cease-fire was declared, "causing material damage and threatening the life and health of Russian citizens."
The loudest response to that episode came hours before Mr. Putin's statement, when the Russian defense minister, Sergei K. Shoigu, announced that about 65,000 troops across central Russia would begin a week of combat drills.
In Ukraine, Mr. Poroshenko addressed the nation on Saturday, laying out the details of his 15-point peace plan and speaking as if the military fight was over. The 12-minute speech emphasized the need for negotiations, addressing the main Russian criticism.
"I am ready for dialogue with those who made a mistake, having mistakenly supported the position of separatism," he said, adding "except, of course, those who are complicit in terrorist actions, murders and torture."
He left at least a partial window for talks with some of the separatists who have not taken up arms. But the separatist political leaders have said they would only talk to Kiev via intermediaries.
So the crux of the problem remains that the two sides that most need to hammer out a compromise refuse to meet. It appeared unlikely that the differences over who would participate could be bridged quickly.
Russia's dual-track approach reflected what analysts have been saying for weeks is Russia's main goal: to put pressure on the Ukrainian government to grant significant autonomy to the southeast without prompting a third round of Western sanctions. Western leaders are set to consult on further sanctions this week.
But it also reflected the split within the Russian government. The military and nationalists pushed Mr. Putin to annex the autonomous Ukrainian region of Crimea in March and generally want Russia to reclaim its role as a global power and an antidote to the West. More liberal economists, business moguls and diplomats, recognizing that Russia is now integrated into the world economy in a way it never was during the Soviet era, want to prevent even worse fallout than that caused by Crimea's annexation.
"I think that they will keep agreeing to cease-fires, keep calling on the militants to stop the fighting and keep supplying the militants with arms until they achieve a stable equilibrium on their terms," said Clifford Kupchan, a Washington-based Russia analyst at the Eurasia Group.
Analysts believe that Russia is looking, eventually, for a compact. But it wants sufficient influence in southeastern Ukraine to destabilize the Kiev government or to make sure that it does not get too close to the European Union or contemplate joining NATO.
Analysts point out that there is insufficient trust on either side to negotiate, and that the fighting might slip out of the leaders' control.
"Each side is escalating, hoping the other side will blink, but in the process it is getting harder and harder for any kind of meaningful agreement to be reached," said Mark Galeotti, an expert on Russia's security forces at New York University.
Mr. Putin emphasized the need for such an agreement in his announcement. "The opportunity that opens up with the end of hostilities should be used to start constructive negotiations and to reach a political compromise between the parties to the conflict in southeast Ukraine," his statement said.
In May, Mr. Putin had suggested that the rebels not hold a referendum on separating from Ukraine, but they ignored his call.
Mr. Poroshenko declared the cease-fire as he introduced a 15-point peace plan that would establish a six-mile demilitarized zone along the Ukrainian-Russian border and provide an escape corridor for Russian and Ukrainian mercenaries who the Ukrainian government has said are involved in the fighting. It suggested the regions would be granted autonomy, a key Russian demand, although critics said it did not go far enough.
Military and political leaders of the self-declared people's republics in the Donetsk and Luhansk regions of eastern Ukraine on Saturday rejected laying down their arms.
Alexander Borodai, the Russian prime minister of the Donetsk People's Republic, said "there is no cease-fire" and called for peacekeepers from Russia to enter the country to prevent "a humanitarian catastrophe."
"How can I comment on a plan that is only a fantasy?" Mr. Borodai said when asked if he was aware of the peace plan.
Neil MacFarquhar, The New York Times. Andrew Roth contributed reporting from Donetsk, Ukraine.