In late May, Russia and Kazakhstan agreed to launch the union on July 1 without Belarus after negotiations with Minsk stalled when Moscow refused to abolish export duties on the oil.
"It will be either a triangle between Russia, Kazakhstan and Belarus or just Russia and Kazakhstan," Shuvalov, Russia's pointman for the custom's union negotiations, told participants of the Renaissance Capital investment conference.
The decision on the number of countries involved will likely be taken in Kazakh capital of Astana on July 5, he added.
Belarus has said on numerous occasions that it is ready to join the entity as well as of July, but said it would not back down on energy prices.
Relations between Moscow and Minsk soured further in recent weeks over gas supply and transit prices to Belarus.
The new trading bloc is expected to boost Moscow's influence in the region but could complicate World Trade Organization (WTO) membership talks, which Russia has been trying to join for for more than a decade and a half.
Shuvalov reiterated Moscow's stance that the union was not going to interfere with Russia's WTO negotiations. The customs union is based on the fundamental principles of the WTO and those of the European Union, he said. (Reuters)
