Ukraine, Georgia, and Moldova have signed key economic and political accords with the European Union in Brussels.
Ukraine signed an agreement on closer economic ties with the EU, as did Moldova and Georgia, which also signed documents on closer political ties.
The moves represent a big step toward the West and away from Russia for the three countries.
European Council President Herman Van Rompuy said that "future generations will remember this day." He said the European Union now stands by the three countries "more than ever before."
Both Van Rompuy and European Commission President Jose Manuel Barroso stressed that the accords were not aimed at harming Russia. Barroso said the EU was not seeking an exclusive partnership with the three countries, and that the agreements were "for something and not against anybody."
Georgian Prime Minister Irakli Garibashvili said becoming a member of the European family was Georgia's "unwavering will." He said the June 27 signing ceremony was "the beginning of a great journey."
Garibashvili said Abkhazia and South Ossetia -- Georgian breakaway regions recognized as independent states by Russia -- would also see the advantages of closer ties with the EU.
Moldovan Prime Minister Iurie Leanca said the accords offered his country "a future." He said that Moldova had made a "definitive choice," and that choice is European integration.
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Ukrainian President Petro Poroshenko said the signing of the agreements may be the "most important day" for his country since it became independent from the Soviet Union.
He said, "over the last months, Ukraine has paid the highest possible price to make its European dream come true."
He also declared that Ukraine's ultimate goal was to join the EU when it is "fully prepared."
Former President Viktor Yanukovych's abrupt refusal to sign the agreements back in November 2013 sparked the Euromaidan revolt that led to his ouster in February.
Before the signing, Poroshenko help up a pen, saying it was the pen Yanukovych was supposed to use to sign the Association Agreement at the EU summit in Vilnius in November.
"Historic events are unavoidable," Poroshenko said.
In March, the EU and Kyiv signed an Association Agreement after Russia's annexation of Crimea.
Brussels had planned to sign the political and trade pacts with Chisinau and Tbilisi later this year but moved up the date amid concerns Moscow may try to obstruct the process.
Russia has threatened to respond with trade barriers as it pushes its own Eurasian Economic Union.
In comments to Interfax on June 27, Russian Deputy Foreign Minister Grigory Karasin warned of "serious consequences" for the signatories.
He said, however, that "the signing of such a serious document is, of course, a sovereign right of any state."
Russian President Vladimir Putin's spokesman, Dmitry Peskov, reiterated on June 27 that Moscow will take measures in case the signing of the EU accords by the three former Soviet republics has negative effects on Russia's economy.
Among other things, the agreements will allow the three countries unfettered access to the EU's market of 500 million consumers.
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With reporting by Reuters, AFP, and RIA Novosti