"(This) recognizes the aspirations of the people of Ukraine to live in a country governed by values, by democracy and the rule of law, where all citizens have a stake in national prosperity," he said.
Two sets of the documents were passed around the table for the EU's leaders and Yatseniuk to sign in a solemn atmosphere. Van Rompuy and Yatseniuk then shook hands and exchanged the documents to applause, witnesses said.
Coinciding with the signing in Brussels, Russia's upper house of parliament unanimously approved a treaty annexing Ukraine's Crimea region, clearing the way for President Vladimir Putin to sign it into law.
Yanukovich turned his back on signing the EU agreement last November in favor of closer ties with Moscow, prompting months of street protests that eventually led to his fleeing the country. Soon afterwards, Russian forces occupied Crimea, drawing outrage and sanctions from the United States and EU.
(Read more: Europe adds 12 names to Russia sanctions, plans broader move)
As well as the closer political ties, the European Commission has agreed to extend nearly 500 million euros worth of trade benefits to Ukraine, removing customs duties on a wide range of agricultural goods, textiles and other imports.
Once Ukraine has held presidential elections on May 25 and a new administration is in place, the EU plans to move ahead with signing a free-trade agreement with Ukraine, giving the country unfettered access to the EU's market of 500 million consumers.
That has far more potential to strengthen Ukraine's shattered economy, but also runs the risk of provoking retaliatory steps from Russia, which has already imposed stricter customs checks on trade with Ukraine.
The other burden for Kiev is meeting the obligations that come with EU political association, including instituting changes to the rule of law and justice, and adopting business and environmental standards that will require hard work and long-term investment to meet.
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