Ukraine signed a landmark free-trade agreement with the European Union on Friday, a move that immediately drew an angry response and a threat of “grave consequences” from Moscow.
The economic pact — the abandoned signing of which last year sparked protests that led to the ouster of then-President Viktor Yanukovich and months of unrest — holds the prospect of deep economic integration and unfettered access to the EU's 500 million citizens.
But Russia has long been opposed to its neighbor’s acceding to the EU treaty, amid concern from Moscow over losing influence over former Soviet republics. Georgia and Moldova signed similar deals on Friday.
Also on Friday, Russian President Vladimir Putin again said a long-term cease-fire was needed in Ukraine to allow talks between the Kiev government and representatives of eastern regions where rebels are waging an armed insurgency against the pro-Western government.
Ukraine's President Petro Poroshenko signaled he would make a decision on extending a cease-fire in the east when he returns to Kiev on Friday after an EU summit in Brussels.
"This decision will be taken by me when I return to Ukraine. I will have to conduct consultations with the minister of defense, the defense council," Poroshenko told a news conference. "The decision will be taken today."
Ukraine, Georgia and Moldova have made clear their ultimate goal is membership in the EU, but Brussels, under pressure from voters weary of the bloc’s expansion, has made no promise it will extend them invitations.
The EU and Ukraine had already signed parts of the agreement dealing with political cooperation in March, but the more significant economic chapters were left to be signed after the country’s presidential elections.
As part of the deal, the EU will insist that Ukraine meet its standards on human rights and democracy, fights corruption, strengthens the rule of law and reforms its economy.
Kremlin spokesman Dmitry Peskov said Russia would take measures to protect its economy if it is negatively affected by the agreements, Russia’s RIA news agency reported.
"As soon as the implementation starts, there can be talk of some protective measures," he said. "Everything needed to protect our economy will be undertaken."
European Council President Herman Van Rompuy said there was nothing in the agreements that would harm Russia in any way.
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 afterward, Russia annexed Ukraine's Crimean Peninsula, drawing outrage and sanctions from the United States and the EU, and pro-Russian separatists began an uprising in eastern Ukraine that has claimed hundreds of lives.
Months of turmoil prompted some Ukrainians to abandon the country. The U.N. said Friday that 110,000 Ukrainians had fled to Russia this year and another 54,000 fled their homes but stayed in Ukraine as the government fought with separatists in the mostly Russian-speaking east.
"Over the last months, Ukraine paid the highest possible price to make her European dreams come true," Poroshenko told EU leaders at a signing ceremony in Brussels, calling it the most important day for his country since independence from the crumbling Soviet Union in 1991.
Poroshenko urged the EU to reward Ukraine for its sacrifices by promising the country would be eligible for membership of the EU once it was ready. The pledge would “cost the EU nothing but would mean the world to my country,” he said.
Van Rompuy said the agreements with the three countries were "not the final stage of our cooperation," but this fell short of the prospect of ultimate EU membership.
Moldovan Prime Minister Iurie Leanca has also set his sights on EU membership, saying on Thursday that he hoped his country would apply to join in the second half of 2015.
Russia, which fought a five-day war with Georgia in 2008, has met previous attempts by its neighbors to move closer to the EU with trade reprisals, and EU officials fear the same thing could happen again.
EU officials say that, in diplomatic talks, Russia has threatened to withdraw the duty-free treatment that Ukraine currently benefits from as a member of the Commonwealth of Independent States free-trade pact.
Last year Russia briefly imposed onerous customs checks at the Ukraine border and responded to Moldova's overtures to Brussels by cutting off imports of Moldovan wine.
Russian energy giant Gazprom cut off gas supplies to Kiev last week after Ukraine failed to pay its gas debts.
Al Jazeera and wire services