VIENNA (AFP) - Ukrainian President Viktor Yanukovych vowed Thursday that his country would continue to work towards EU membership even as Kiev halted preparations to sign a historic trade deal with Europe.

Ukraine "will work further on this path, this path to EU integration," Mr Yanukovych said on a visit to Austria, speaking through a translator. His comments came as Ukraine's government issued a decree ordering the "halt of the process of preparing the Association Agreement between Ukraine and the European Union".

Securing the Association Agreement is seen as the first step to obtaining EU membership. However, the bloc has demanded the release of jailed opposition leader Yulia Tymoshenko in exchange for the agreement. Earlier Thursday, the parliament in Kiev voted against bills that would free Mrs Tymoshenko, the 2004 Orange Revolution co-leader.

"Of course there are difficulties on the path," Mr Yanukovych told journalists after meeting with his Austrian counterpart Heinz Fischer."We need to examine these problems and see if they can be solved or avoided," he added, insisting the Ukrainian parliament has passed on Thursday several other bills to fulfill EU criteria.

Asked why Mrs Tymoshenko, who suffers back problems and has been offered medical treatment in Germany, could not be released, Mr Yanukovych insisted this was a decision to be taken by the courts.

"To answer this question definitely today is impossible," he said, pointing to the widely opposing views of Mrs Tymoshenko in the Ukrainian parliament and abroad.

"We must stick to the law. We respect the law and the constitution. A release of Mrs. Tymoshenko is very controversial and contradictory," he added. Mrs Tymoshenko, a former prime minister and arch-rival of the president, was jailed in 2011 for seven years on charges of abuse of power while in office.

Critics have accused Yanukovych of trying to keep her out of politics ahead of presidential elections in 2015.