Independent analysts doubt the idea will get off the ground.
"A currency union would be a bad mistake in many ways. Luckily, we can be confident that Belarus and Kazakhstan will never agree to it," said Christopher Granville, managing director of consultancy Trusted Sources in London.
"Lukashenko did in fact sign up to a monetary union with Russia in the 1990s and spent the best part of a decade wriggling out of that commitment since he realised that it meant the end of Belarusian sovereignty."
The three leaders made clear it would be a tough year for countries in the Eurasian Economic Union, the Russia-led political and economic bloc they have formed with Armenia, with Kyrgyzstan set to join later this year.
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Putin's dream of the Eurasian Economic Union matching the economic muscle of the European Union, the United States and China is a long way from fruition, though it has an integrated single market of more than 170 million people.
The fall in oil prices and Western economic sanctions over Ukraine have worsened an economic slowdown in Russia, and the rouble has declined by about 40 percent against the dollar since midway through last year.
Belarus devalued its own rouble in January and there has been speculation on markets that Kazakhstan may soon devalue its currency, the tenge, little more than a year after a more than 19 percent devaluation.
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