KIEV, Aug. 21 – The Customs Union of Russia, Belarus and Kazakhstan will be forced to step up customs procedures for Ukraine and may withdraw from a free trade area with the country if Kiev signs an agreement on association and free trade area with the EU, Russian presidential advisor Sergei Glazyev said.

"The matter of ending the free trade relations with Ukraine may be raised, the Eurasian Economic Commission is already studying this issue," Glazyev said in an interview with the Vesti newspaper.