Ukraine should decide whether to join the Belarusian-Kazakh-Russian Customs Union or the European Union, says Lithuanian President Dalia Grybauskaite.

"It is impossible to sign both, and so the country should choose," Grybauskaite said at a joint press conference with Ukrainian President Viktor Yanukovych in Vilnius on Wednesday.

At the same time, an association agreement with the EU will absolutely not prevent Ukraine from trading with Russia and the other Customs Union members, Grybauskaite said.

"But formally the signing of an association agreement means that it cannot be compatible with the agreements with the Customs Union," she said.

Yanukovych said in commenting on the issue, "As for the Customs Union, this institution exists, and it is necessary to look for possibilities and models for cooperation with it. And we are also working on this."

Yanukovych pointed out that trade turnover between Ukraine and the Customs Union countries reaches $60 billion, "and we cannot disregard this."