Tymoshenko made the call in a letter on Friday, a day after Ukraine Prime Minister Mykola Azarov issued a decree announcing the halt in negotiations over the landmark trade and political pact. The Association Act was due to be signed in Lithuania on November 28-29, and would have represented a significant step towards Ukraine's eventual European Union membership.

Ukraine had found itself in a tug-of-war between the EU and Russia, its historical ally, over the signing of the deal. Allowing Tymoshenko to travel to Germany as part of medical treatment - a key condition of the agreement - was another sticking point.

In a letter read out by her lawyer, Tymoshenko urged Ukrainians to take to the streets to make their feelings known. Jailed in 2010 on abuse of power charges, Tymoshenko said signing the EU deal was the “only chance to survive as a politician” for President Viktor Yanukovych - her long-time political rival.

Putin speaks out on reports of influence

Ukraine's decision to back away from the deal on Thursday came just hours after Putin suggested three-way talks with the EU. There had been talk Russia had pressured Ukraine not to sign the EU pact, threatening economic consequences if it was ratified.

Putin, however, said it was the EU - not Russia - that had attempted to bully Ukraine.

"We heard threats from our European partners with regard to Ukraine that range up to the promotion of mass protests," Putin told reporters in St Petersburg. "This is pressure and this is blackmail," he said.

Ukraine has indicated it will now "renew active dialog" with Russia, other members of a Moscow-led customs union and the Commonwealth of Independent States, a grouping of former republics of the Soviet Union.

Stefan Füle, the EU's Neighborhood Relations Commissioner, said the “door remains open” for Ukraine: "We have not fully given up, as we were not actually officially informed by the Ukrainian side that the signature is impossible at Vilnius," he said.

"It's the best offer Ukraine could get at this point in time to modernize their country,” Füle said. The EU has set no deadline for the signing of any deal, although Füle indicated an EU-Ukraine summit in 2014 would be the next opportunity to do so.

ph/msh (AFP, dpa)