Russian President Vladimir Putin arrived in the Kazakh capital on Thursday where he was set to sign a deal with his Kazakh and Belarussian counterparts creating a new economic union championed by Moscow.
Putin, Belarussian President Alexander Lukashenko and Kazakh President Nursultan Nazarbayev were due to sign the document in Astana following talks on Monday.
The Eurasian Economic Union, which is to come into force on January 2015, is designed to strengthen ties between the ex-Soviet countries which have already joined forces in a customs union created in 2010.
"The three states agree to guarantee free circulation of goods, services, capital and the work force, to agree on policy in key areas of the economy: energy, industry, agriculture and transport," the Kremlin said in a statement.
"This completes the formation of the largest shared market on the CIS area (170 million people), which will be a new powerful centre of economic development," the Kremlin said, referring to the Commonwealth of Independent States (CIS) made up of ex-Soviet countries.
The alliance would follow a much looser Eurasian Customs Union that Russia formed with the two ex-Soviet nations in an effort to build up a free trade rival to the 28-nation European Union (EU) bloc.
The economic union project is hugely symbolic for Putin, who in 2005 called the breakup of the Soviet Union "the biggest geopolitical disaster" of the 20th century.
But Putin has crucially failed to secure the hoped-for participation of Ukraine, a country of 46 million with a potentially strong industrial sector.
Ukraine plunged into an unprecedented crisis last November when then-President Viktor Yanukovych pulled out of signing an Association Agreement with the European Union.