Russia and Belarus are working on the unification of their customs duties under a 1996 Union Agreement providing for political, economic and military integration.
Andrei Sotnikov, a member of the Russia-Belarus Union's Standing Committee, said: "The countries would be better off if they joined the WTO with their customs union already in place."
He said they will be unable to preserve mutual trade preferences, crucial to their would-be customs union, if either country enters the WTO before integration is completed.
Sotnikov said the Russia-Belarus customs union could be formed next year at the earliest and that it will take at least as much time to create as the European Union's, which was in the making for a decade.
Once a customs union has taken shape, Russia and Belarus will be able to introduce a single currency, another step toward full-scale economic reintegration, he said.
