President Petro Poroshenko's plan, announced after talks with the leaders of Russia and Germany, would offer separatists in the eastern provinces that form Ukraine's industrial heartland a chance to lay down their weapons or leave the country.
Yet a key question is whether Moscow has the desire and the ability to persuade the pro-Russia insurgents to accept Poroshenko's plan. Rebel leaders have remained defiant, but in a sign of behind-the-scenes maneuvering, some of them visited Moscow this week to meet with senior officials and lawmakers.
Poroshenko didn't say when the cease-fire could be declared, but the country's defense minister, Mykhailo Koval, was quoted as saying it could begin "within days."
The plan could also help ease the worst crisis between Russia and the West since the Cold War, a situation triggered by Moscow's annexation of Crimea in March following the ouster of Ukraine's pro-Russia president.
Russian President Vladimir Putin discussed the possible cease-fire in a phone call with Poroshenko late Tuesday, their offices said, and Poroshenko also spoke with German Chancellor Angela Merkel.
"The plan will begin with my order for a unilateral cease-fire," Poroshenko told reporters in Kiev. "I can say that the period of the cease-fire will be rather short. We anticipate, that immediately after this, the disarming of the illegal military formations will take place."
He said those separatists who lay down arms and haven't committed grave crimes will be granted amnesty.
Putin has welcomed Poroshenko's peace initiative in an apparent hope that de-escalating tensions with the West would help Russia avoid another round of crippling economic sanctions. Still, embracing the plan would require a delicate balancing act for the Kremlin, which is facing rising demands from Russian nationalists to send troops into Ukraine.
Poroshenko said a cease-fire should follow securing the border with Russia, and Ukrainian officials said Wednesday they were completing the effort. Despite their optimistic statements, sealing the 2,000-kilometer (1,240-mile) border could be a challenging task for the nation's ill-equipped and badly organized armed forces.
Russia has denied Ukrainian and Western claims that it was fomenting the insurgency by sending troops and weapons, insisting that Russian citizens among the rebels are volunteers.
Poroshenko made repeated promises to restore peace before and after winning May's election but Wednesday was the first time he said government forces will be the first to halt hostilities, which has been Russia's main demand.
Denis Pushilin, an insurgent leader in Donetsk, told Russian independent Dozhd television that Poroshenko's latest offer was "senseless."
"They cease fire, we lay down weapons, and then they will capture us weaponless," he said.
Russia's foreign minister, Sergey Lavrov, speaking in Baku, Azerbaijan, said any cease-fire should be "comprehensive" not temporary. He said if it was followed by negotiations "then it could be the step President Poroshenko has promised and which in general we were all waiting for."
U.S. Treasury Secretary Jacob Lew also expressed backing for the plan during a stop in Jerusalem.
"We call on Russia to support President Poroshenko's peace plan and to cease support for militants and separatists who are further destabilizing the situation and to stop the provision of arms and materiel across the border," he said.
In another move that would help appease Moscow, Poroshenko nominated Pavel Klimkin, the ambassador to Germany, to replace Andriy Deshchytsia as foreign minister. Lavrov had said he would never speak again to Deshchytsia after he used an obscenity to describe Putin as he tried to calm protesters who besieged the Russian Embassy in Kiev last weekend.
An end to fighting and a safe exit for rebels would allow Putin to say that Russia has fulfilled its goal of protecting Russian speakers in Ukraine. Poroshenko, in his turn, also would be able to claim victory over the rebellion.
If Poroshenko's plan succeeds, that would allow him to consolidate his power and help set the stage for the early parliamentary election he wants.
For Ukraine, an end to hostilities in the east is essential as it tries to shore up its economy, which is teetering on the verge of bankruptcy. It's also key to mending the rift between the eastern regions where most residents want close ties with Russia, and the west, where the majority wants a quick integration into Europe.
Any such cease-fire, however, would raise the question of whether the separatists would respect it. While Russia has insisted that it wasn't controlling the rebellion, some of its leaders appear to have high-level connections in Moscow.
Alexander Borodai, a Moscow political consultant, is now the self-proclaimed prime minister of the so-called Donetsk People's Republic, which has declared independence in eastern Ukraine.
On Tuesday, Borodai attended a meeting with members of the Russian parliament's upper house, thanking Russia for "a steady flow of volunteers coming from Russia who fight for the interests of people of Donbass." At the same time, he acknowledged that "part of the Russian establishment does not want Donbass and other regions of Ukraine to join Russia."
The insurgency in the eastern Donetsk and Luhansk regions flared up in mid-April, with rebels, emboldened by Russia's annexation of Crimea, seizing government buildings and declaring independence for their provinces. They have pushed for joining Russia, but Putin has stonewalled their demands.
Ukrainian government forces have struggled to suppress the insurgents, who shot down a military transport plane Saturday, killing all 49 on board. At least 356 people, including 257 civilians, have been killed since May 7 alone in the fighting and 34,000 have fled their homes, according to the U.N.
Nataliya Vasilyeva and Vladimir Isachenkov in Moscow, John Heilprin in Geneva, Frank Jordans in Berlin and Alon Bernstein in Jerusalem contributed to this report.
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