“Russia wants to show that it is in command of what is happening,” said Fyodor Lukyanov, editor of a prominent Russian foreign policy journal. “For Russia, it is important first to prevent the Ukrainians from thinking that they could win militarily, and to accept the separatist leaders as partners in negotiations.”

The details of the peace deal were sketchy at best, entangled in complicated diplomacy and domestic politics. But it was clear from various, somewhat confused and contradictory statements that Mr. Putin and the Ukrainian president, Petro O. Poroshenko, had held an extensive discussion on the issue by telephone early Wednesday.

At first, Mr. Poroshenko’s office issued a vague announcement that the two leaders had agreed to a “lasting cease-fire.” The statement was diluted later to say only that both leaders had endorsed the need for a cease-fire and that Mr. Poroshenko hoped negotiations would begin in earnest on Friday. Mr. Putin said his notes had emerged from the telephone conversation.

In announcing the plan, Mr. Putin said he expected Ukraine and the separatists to wrap up an agreement after a new round of negotiations in Minsk, Belarus, on Friday. Ukraine, Russia and Europe are all party to the talks there, and they include representatives of the separatists. The two-day NATO summit meeting is also scheduled to end Friday.

Aside from the cease-fire, the plan laid out by Mr. Putin called for Ukrainian artillery to pull back and out of range of the eastern separatists’ strongholds; an end to airstrikes; an exchange of all detainees; opening up humanitarian corridors for residents of the separatist areas; repairing damaged infrastructure; and deploying international observers to monitor the cease-fire.

It made no mention of autonomy for the separatist eastern regions, the central political demand that Russia has emphasized since March. That is widely seen as critical to the Kremlin’s long-term goal of maintaining influence over Ukraine’s domestic affairs and blocking any future attempt to join NATO.