Russian oil major Rosneft and U.S. energy giant ExxonMobil signed an agreement on Friday to develop hard-to-recover oil deposits in Western Siberia.

Rosneft head Igor Sechin said before the signing ceremony production of hard-to-recover energy sources could be profitable only if the Russian government approves a bill on tax benefits for production in these areas.

Rosneft owns licenses for hard-to-recover oil reserves of 800 million tons. Potential output in the hard-to-recover areas exceeds 15 million tons per year.

The two companies previously signed a contract to jointly develop offshore hydrocarbon deposits in Russia's Arctic in April. Rosneft and ExxonMobil will establish joint venture firms to explore East Prinovozemelsky Blocks 1, 2 and 3 in the Kara Sea in the Russian Arctic and the Tuapse License Block in the Black Sea. Rosneft will hold 66.7 percent in both joint ventures.

ExxonMobil also signed an agreement on Friday to join a Rosneft-established Science and design center for Arctic offshore development, which would develop the know-how and equipment for offshore projects, including ice drilling and production platforms.