Brussels, Belgium (CNN) -- Ukrainian President Petro Poroshenko on Friday signed a broad agreement of cooperation with the European Union, the same deal whose reversal set off a crisis in the nation. The signing came hours before the President's office announced a three-day extension of a cease-fire. This is the latest step suggesting Ukraine may be moving back from the brink of full-fledged civil war -- though the situation remains volatile, with continued violence and the constant fear of yet more, cease-fire or not. This tension has recent roots in then-President Viktor Yanukovych's decision to shun the EU Association Agreement last year and work with Russia instead. That move unleashed deadly strife that led to Yanukovych's ouster, the loss of Crimea and a pro-Russia separatist rebellion.
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NEW: Ukrainian President's office: Cease-fire is extended 72 hours
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Ukraine's Petro Poroshenko: EU document is "a symbol of faith and unbreakable will"
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The signing shows "how dramatically things can change in a short time," he says
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State media: Vladimir Putin calls for "substantial" talks in Ukraine, end to bloodshed
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Sealing the deal may be the second-most important moment in Ukraine's history, Poroshenko said, after its independence from @placeholder.
EU Association Agreement
Poroshenko said that in signing the @placeholder, he was making a unilateral statement that his country has underlined its choice of future membership in the EU.
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As @placeholder's government works to quell the violence in the east, Poroshenko has said that negotiations with Russian separatists there will continue Friday.
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As Ukraine's government works to quell the violence in the east, @placeholder has said that negotiations with Russian separatists there will continue Friday.
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He made the same point Friday when he said that "all Ukraine, including @placeholder" will be associated with the EU.
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Russia and @placeholder have been engaged in a tense standoff since the annexation in March when Russia also massed troops along its western border with Ukraine.
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At his request, @placeholder's upper house of parliament voted Wednesday to revoke the President's right to use troops in Ukraine.