Armenia, Moldova and Ukraine are the most probable candidates for joining the Russia-Belarus union state in the future. As reported by "Novosti" Russian agency, chairman of the Parliamentary Assembly of the RB union, speaker of the Russian State Duma Gennady Seleznyov said at a briefing in Moscow, devoted to a bill of the Constitutional act of the union state. In his words, other countries' joining of the RB union will be possible just on the basis of the document. G. Seleznyov also reported that each large measure of the Parliamentary Assembly of the RB union was attended by deputies of Ukraine and Moldova. "However, since the first day Armenian parliamentarians have been working with us most actively," - Gennady Seleznyov said.