Gazprom and Italy’s oil and gas company Eni are to start building the South Stream gas pipeline in December.
"Gazprom and Eni aim to make the final investment decision on the offshore part of the project in November and start the construction in December," said a Kremlin statement.
President Vladimir Putin held talks with the Italian Prime Minister Mario Monti on Monday with energy cooperation an important point on their agenda.
South Stream, a Russian-backed rival to a European Nabucco pipeline, is expected to cost more than 15bln euro ($18.25bln). It will export some 63 billion cubic metres (bcm) of gas to southern Europe starting 2015.
Eni said earlier this month it expected the final investment decision in late 2012 or early 2013.
The South Stream consortium also includes France's EDF and Germany's Wintershall. The pipeline will transport some 63 bcm of natural gas from Russia through Bulgaria and on to Italy and Austria.