Faced with pressure from Russia, Yanukovych shelved plans for closer ties with the EU last week. The move sparked protests at home and set back EU plans to pry a nation of 46 million people loose from Moscow's orbit and push its geopolitical clout right up to Russia's border. Instead, Moscow would like Kiev to join a separate union that aims to rival the EU.
Still, the EU has not given up and continues to laud the benefits of Ukraine having closer ties with the world's biggest trading bloc, and has said the deal could be signed any time after the summit.
"The door is still open," Swedish Prime Minister Fredrik Reinfeldt said.
Polish Foreign Minister Radoslaw Sikorski said Ukraine's economic prospects would greatly improve if it signs the deal.
"The more you are willing and able to accept our assistance in modernizing your institutions, the more generous we are," Sikorski said.
Ukraine remains careful not to burn anymore bridges with the EU at the summit.
"I am sure that the decision at tomorrow's summit will be positive. We will find a solution," Ukraine's first deputy prime minister, Serhiy Arbuzov, said in a comment that may indicate that the suspension of the signature wasn't final.
While facing pressure from the EU, Yanukovych is grappling with discontent at home. Thousands of people have kept up daily protests in Ukraine's capital against Yanukovych's decision to drop further EU integration for closer ties with Russia. Popular mass protests in 2004, known as the Orange Revolution, brought down Yanukovych, and he is wary of a repeat of the same scenario now.
The protesters have been calling for the release of jailed former Prime Minister Yulia Tymoshenko.
The EU has made Tymoshenko, the political rival of Yanukovych, and an end to selective justice in Ukraine a condition for signing the association agreement.
But Tymoshenko herself has urged European leaders to ink the deal with Ukraine without linking it to her release.
Tymoshenko's daughter Eugenia told The Associated Press in an interview in Vilnius that "it's not political prisoners who need to be saved now, but Ukraine needs to be saved".
Analysts believe that Yanukovych is trying to play both sides, while attempting to secure a better short-term deal with Moscow.
"The Yanukovych line at Vilnius seems to be to play for time-keep options open, and come away with something which he can then use in negotiations with Russia likely next week over a gas financing deal," said Tim Ash, chief emerging-markets economist at Standard Bank in London.
"He probably hopes he can get enough `warm words' from EU leaders in terms of the EU integration process to calm the mood on the streets, and take momentum out of street demonstrations," Ash added.
Though Ukraine remains the focus at the summit, officials finished off the technical initialing of similar agreements with another two former Soviet republics, Georgia and Moldova, which have populations of 4.5 million and 3.6 million, respectively.
- AP