The price of the natural gas Russia's gas export monopoly sells to Europe on long-term contracts could fall to around $370 per 1,000 cubic metres in 2013 from over $400 this year.
"This (price) is a base-case scenario. The forecast is subject to change during the course of the year," the source said on Tuesday.
The source said gas exports to Europe are expected to increase to 152 billion cubic metres (bcm) next year from just over 140 bcm in 2012, which came in below forecasts due to sluggish demand.