Russia is to build a nuclear power station for Belarus and provide the $9.4 billion required as a loan to its smaller neighbor.
Russian Prime Minister Vladimir Putin oversaw the signing of a deal in Minsk on Tuesday that foresees a two-block facility coming fully online by 2018.
Its location, near Belarus' border with Lithuania, has caused concern with environmentalists in the Baltic country as well as at home.
Putin suggested in a televised meeting with Belarusian President Alexander Lukashenko that the power station would be safer than the Japanese plant crippled by an earthquake and tsunami.
The export of Russia's nuclear expertise is a key income source for the government, with contracts signed with several countries in recent years.
(This version CORRECTS country on border.)