South Stream would split with arteries headed to southern Europe after passing through Turkish waters of the Black Sea. It would carry roughly 2.2 trillion cubic feet of gas per year when it goes into service by 2015.
Moscow aims to find new ways to get natural gas to European consumers. Disputes with Ukraine, which hosts the bulk of Russia's gas bound for Europe, makes traditional routes risky.
Gazprom last week said it was bypassing Austria and would terminate South Stream in northern Italy. Austria, the company said, will no longer play a role in the project, even though agreements were reached with Austrian energy company OMV last year.
Both sides said they "appreciated the progress" of South Stream.
Gazprom, in a statement, said Italy was one of its major partners in Europe, noting it has a "long-standing partnership" with Eni.
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