Russia and Kazakhstan have launched a customs union in an effort to boost trade and investment between them.
Russian Prime Minister Vladimir Putin told a government session that Belarus was still welcome to join, saying Moscow was seeking "full-fledged, mutually beneficial cooperation" with Minsk.
Belarus has not yet ratified all the necessary documents to join the customs union.
Minsk has linked the ratification of the documents with a demand that Russia cancel export duties on oil.
compiled from agency reports