In the tensions over whether Ukraine will move closer to the European Union or be pulled toward Moscow, the most vivid figure may be the one who's least seen — former Prime Minister Yulia Tymoshenko, who turned 53 in a prison cell Wednesday.

The woman known worldwide for her elaborately braided blonde tresses and for her emphatic rhetoric in the Orange Revolution had been seen as the major impediment to Ukraine's signing a landmark association agreement with the EU. Bloc officials condemned her imprisonment as a case of political revenge and made inking the pact conditional on her release — a demand that President Viktor Yanukovych has been reluctant to fulfill.

But now that Yanukovych says Ukraine is halting integration efforts because the economic burden would be too high, Tymoshenko appears to have lost significant leverage to get out of prison before her sentence expires nearly five years from now.

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WHO SHE IS

In the 2004 Orange Revolution mass protests that overturned a fraudulent presidential election, Tymoshenko was more prominent than Viktor Yushchenko, the candidate who'd been cheated. Her combination of haute couture dresses and peasant braids caught the cameras' attention and her pungent speeches thrilled the crowds. She became widely seen as an icon of democratic reform in the former Soviet Union.

But once Yushchenko became president in an election rerun and appointed Tymoshenko as prime minister, she showed another side. The two leaders quarreled bitterly, with Yushchenko accusing her of serving the interests of some businesses. The accusations reminded many of Tymoshenko's controversial past as head of the main importer of Russian natural gas and as an associate of then-Premier Pavlo Lazarenko, now imprisoned in the U.S. for money-laundering and extortion.

She returned to the premiership in 2007 and in 2010 narrowly lost the presidential election to Yanukovych, the arch-foe of the Orange Revolution.

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IMPRISONMENT

Tymoshenko was convicted and sentenced to seven years in 2011 for misusing her power in signing a 2009 deal with Russia that doubled the price Ukraine paid for natural gas. Her supporters and many Western officials say the case was revenge by Yanukovych, whom she openly detested. The deal resolved the gas crisis that afflicted much of Europe during the depths of winter that year, when Russia stopped selling gas to Ukraine, thereby reducing the amount flowing through Ukraine to downstream customers in the West.

In prison, she has consistently complained of severe back pain and inadequate treatment.

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THE EU'S DEMAND

The bloc is eager to expand its influence eastward by closer relations with Ukraine, a country of 48 million with rich farmland and extensive industry. But it's unsettled by Ukraine's chaotic politics, its dubious courts and complaints of human rights violations. Making Tymoshenko's freedom a condition for the association agreement was a dramatic way of highlighting the EU's concerns about Ukraine and allowed the bloc to portray itself as a constructive force for reform. As releasing Tymoshenko began to appear out of the question, the EU was still eager enough to embrace Ukraine that a compromise was floated that would allow her to be flown to Germany for medical treatment. But the Ukrainian parliament declined to consider such a measure.

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WHAT'S NEXT

Although Yanukovych will go to Friday's EU summit in Vilnius, Lithuania, where the association agreement was hoped to be signed, he has effectively turned his back on the bloc for now in favor of better relations with Russia. That substantially turns down the pressure to release Tymoshenko, and Yanukovych otherwise has little to gain from doing so. Presidential elections come in 2015 and he wouldn't want his charismatic and tactically adept opponent on the loose to mount another challenge. Meanwhile, prosecutors have said they have reason to file murder charges against Tymoshenko in the 1996 killing of a parliament member; although the charges have not been filed, the prospect of more trouble in court hangs heavy over Tymoshenko.

In turn, the EU would appear to have little to gain and much to lose by turning down the volume of its calls for Tymoshenko's release; that would undermine the bloc's image of being principled defenders of human rights. Yanukovych and his prime minister, meanwhile, have made it clear that Ukraine wants more aid than the EU appears willing to give.