Russian energy giant Gazprom signed a purchase agreement for Turkmen gas during a meeting in Ashgabat between Medvedev and his Turkmen counterpart, Gurbanguly Berdimuhamedov.
Both sides agreed to work on the construction of pipelines to transport natural gas from fields in the Turkmen waters of the Caspian Sea and Kazakhstan.
Russia, Turkmenistan and Kazakhstan in 2007 agreed to develop the Pre-Caspian gas pipeline system.
The East-West gas pipeline, meanwhile, would make Turkmenistan a regional gas transmission center.
Moscow this week hailed the inauguration of a 1,138-mile pipeline meant to deliver gas from Turkmenistan to China, describing the project as an important contribution to global energy security.
The pipeline starts at the Turkmen border with Uzbekistan and then through Kazakhstan to the Xinjiang region in northwest China. A second leg of the pipeline goes into operation in 2010.
Turkmenistan had supplied most of its gas to Russia, though that relationship soured in April following a pipeline explosion that Ashgabat blamed on Russian energy giant Gazprom.
Gazprom said the Ashgabat meeting underlined the "constructive nature" of bilateral ties, strengthening the "long-term partnership in the energy sector" of both countries.