By Luke Baker and Richard Balmforth
BRUSSELS/KIEV (Reuters) - The European Union criticized Russia on Monday for pressurizing Ukraine to reject an EU trade deal, while police fired tear gas at pro-Europe protesters in the former Soviet republic, torn once more between East and West.
Ukraine had been expected to sign a far-reaching trade and political association agreement with the EU at a summit in Vilnius on Friday, the biggest prize in Brussels' efforts to draw states in the former Communist East closer to the EU fold.
But it suddenly announced last week it had decided instead to seek closer trade relations with Moscow.
The decision followed months of Russian pressure, including threats to cut off Ukraine's gas supplies and impose trade restrictions. Moscow has accused the European Union of putting the squeeze on Kiev, too.
Protests have since broken out on the streets of Kiev, with tens of thousands of people demonstrating in favor of closer ties with the European Union, the biggest outpouring since its pro-democracy Orange Revolution nine years ago.
In unusually firm language on Monday, the EU's two most senior officials, European Council President Herman Van Rompuy and European Commission President Jose Manuel Barroso, denounced Russia's actions and said the EU offer remained open.
"The European Union will not force Ukraine, or any other partner, to choose between the European Union or any other regional entity," they said in a joint statement.
"We therefore strongly disapprove of the Russian position and actions in this respect."
Ukrainian President Viktor Yanukovich, acting to defuse the street protests, said the decision had been difficult but unavoidable -- a reference to complaints from Kiev that EU rules were tough on the fragile economy -- and pledged to create "a society of European standards".
"My policies on this path always have been, and will continue to be, consistent," he said in a television address which did not mention relations with Russia or refer to EU pressure to release opposition leader Yulia Tymoshenko.
Tymoshenko's lawyer told about 4,000 demonstrators gathered in Kiev on Monday evening that she had launched a hunger strike to persuade Yanukovich to change his mind.
"As a sign of unity with you, I declare an unlimited hunger strike with the demand to Yanukovich to sign the association agreement," the 52-year-old Tymoshenko in a message to the protesters read out by her defense lawyer, Serhiy Vlasenko.
The turnout was smaller than Sunday's but police clashed with demonstrators and, in a brief incident, fired teargas.
Some saw the protests as part of a wider struggle in a country that houses both native Ukrainian and Russian speakers and which many Russians see as culturally part of their nation.
"I have turned out for revolution because I have understood that the promises of Yanukovich to go into Europe were just pure comedy," said Anatoly Gurkalyuk, 33, a builder.
At the end of last week, the EU appeared minded to quietly accept Ukraine's decision to back away from the trade deal. But the protests - with their hallmarks of Ukraine's 'orange' democracy drive of 2004-2005 - look to have spurred the EU into a renewed effort to court Ukraine.
"It is up to Ukraine to freely decide what kind of engagement they seek with the European Union. Ukrainian citizens have shown again these last days that they fully understand and embrace the historic nature of the European association," the joint EU statement said.
While it seems unlikely Yanukovich will change his mind between now and the Vilnius summit, he might still attend the event, which includes a dinner with EU leaders on Thursday night. He did say whether he would go in his Monday address.
EU officials said the occasion might be an opportunity for German Chancellor Angela Merkel, Britain's Prime Minister David Cameron and French President Francois Hollande, to convince him of the benefits of looking West, even if he doesn't budge now.
It remains unclear what Russian President Vladimir Putin said to Yanukovich to convince him to turn away from the EU.
Diplomatic sources in Moscow, Kiev and Brussels have indicated it probably involved a combination of threats to withdraw political support, targeted economic pressure and the inducement of cheaper Russian gas.
Russia set up its own customs union with Belarus and Kazakhstan in 2010 and wants Ukraine, as well as other former Soviet republics, to join it. Ultimately, it sees the customs union as an alternative to the 28-member European Union.
COSTS AND BENEFITS
Yanukovich's prime minister reproached the EU for pressing Ukraine to fulfil reform criteria, including releasing Tymoshenko. Mykola Azarov said the IMF's refusal to soften its terms for fresh financial assistance had been 'the last straw'.
EU officials have said Russia told Ukraine that introducing EU rules would have cost as much as $100 billion, while Russia cutting off trade would have hurt the country to the tune $500 billion, although it is not clear over what period.
At the same time, while an EU free-trade deal might help Ukrainian business and growth over time, it is not a first step towards EU membership, the ultimate prize. And it was not clear whether signing up with the EU would have done much to bolster Yanukovich's reelection hopes in 2015, either.
One of the many issues Brussels wanted Yanukovich to resolve before signing the deal was the imprisonment of former prime minister Tymoshenko, a bitter Yanukovich rival and a potential election challenger.
Now Ukraine has backed away, there is less pressure on Yanukovich to meet demands to free Tymoshenko and end "selective justice", or to get to grips with the widespread corruption that the EU regards as plaguing Ukraine.
The EU's statement indicates more than anything a desire to remain open and put an end to the sense of a zero-sum game with Russia over the vast country wedged between the two.
(Writing by Luke Baker; additional reporting by Pavel Polityuk and Natalya Zinets in Kiev; editing by Philippa Fletcher)