An advisor to Russian President Vladimir Putin, Sergei Glazyev, believes that Ukraine will be to blame for any aggravation in Russian-Ukrainian relations in gas supply matters ahead of the upcoming signing of the EU-Ukraine Association Agreement.

"Here one can speak about two scenarios only: either everything remains as it is, or should Ukraine want to return to a common economic space with Russia, it will be able to get gas at half the price Belarus does. Any tougher stance may come only from Ukraine. Meaning that some hotheads are urging the Ukrainian authorities to switch to mythical alternative fuel supplies. But one can hardly expect any major changes, as there are no sources other than Russian ones," Glazyev said in an interview with the Vesti newspaper.

When asked whether Russia plans a more rigid diplomatic policy towards Ukraine if Kyiv signs the agreement with the EU, the Russian presidential advisor said that all future relations depend on the choice of the Ukrainian leadership.

"If Ukraine signs the association agreement with the EU, it will cease to be a subject of international law in a whole array of trade and economic relations, as it will hand over the sovereign functions of regulation of international trade, customs, and technical regulations to Brussels," Glazyev said.

"The legal basis for direct dialogue between Kyiv and Moscow will vanish. And we will have to discuss all the matters of trade relations with Ukraine, not with Kyiv, but with Brussels. This is currently happening in the relations with the Baltic states, the Czech Republic, Slovakia, and Hungary. Full EU members can influence something, but Ukraine will not be a full member, it will carry out directives from Brussels, but will not have a say. And there will be aggravation [in relations], which will take place in a completely different plane – between the Customs Union of Russia, Kazakhstan and Belarus and the European Union," Putin's advisor said.