Leonid Chugunov, a top project manager for Gazprom, lead a delegation to Serbia to sign off on the country's final investment decision in the South Stream natural gas pipeline.
"Transitioning to the investment stage at the Serbian section, ahead of all the other countries, will provide new opportunities for the national economy growth as well as secure a long-lasting benefit related to our participation in the project," he said in a statement.
The project should attract as much as $1.9 billion in direct investments for Serbia, Gazprom said.
Dusan Bajatovic, director general of state-owned energy company Srbijagas, said preparations for the project's construction would start soon, adding South Stream was a "project of national significance."
South Stream is one of Gazprom's options to diversity its gas transit network in Europe. The pipeline is designed to carry as much as 2.2 trillion cubic feet of natural gas to Europe each year.
Gazprom exported more than 49 billion cubic feet of natural gas to Serbia in 2011.