Ukraine urges Russia to accept 'reality' on EU relations

He added: "The whole world is changing, the global system of economic relations. But to build a fence to protect yourself from changes using artificial barriers is simply pointless."

Earlier this month Russia imposed extra customs checks on Ukrainian imports for several days, causing a near standstill at the border.

Russian President Vladimir Putin also warned Ukraine that the Customs Union - a Russia-led trade bloc with Belarus and Kazakhstan - might take "protective measures" if Ukraine goes ahead with the EU move.

Launched in 2010, the Customs Union aims at establishing a more political Eurasian Union by 2015 in what some critics describe as an attempt by Moscow to recreate a Soviet-style bloc.

Meanwhile, two Ukrainian opposition leaders, Vitali Klitschko and Arseniy Yatsenyuk, visited Brussels this week to prepare the ground for an EU summit with post-Soviet countries in Vilnius in November.

Speaking after a hearing of the European Parliament's foreign affairs committee, German centre-right MEP Elmar Brok, its chairman, noted that Ukraine's future "should be decided in Kiev, not Moscow or Brussels."

Brok added that Russia's threats of economic sanctions are a breach of World Trade Organisation rules.

Ukraine hopes to sign the political association and free trade pact at the Vilnius event.

But deputies warned that the step is conditional on Ukrainian President Viktor Yanukovych addressing the use of selective justice, ensuring the political neutrality of the prosecutor general's office and releasing former PM Yulia Tymoshenko from jail to receive medical attention in Germany.

Under the EU treaties, the support of a majority of MEPs is required before the association agreement can enter into force.

The Lithuanian government, which currently holds the Union's rotating six month presidency, has identified the EU-Ukraine pact as a top priority.

The move is part of the EU's so-called Eastern Partnership policy, launched in 2009, which aims to build closer relations with Armenia, Azerbaijan, Belarus, Moldova and Ukraine.

The agreements do not offer the prospect of accession to the EU, but the Union is keen to use access to its markets, as well as prospects of visa-free travel, to stimulate political reform.