WASHINGTON, Jan. 1 (Xinhua) -- The United States urged Russia and Ukraine to resolve their natural gas disputes through negotiations on Thursday.

    "We hope that Russia and Ukraine can resolve their dispute over the gas debt and the terms of their natural gas supply arrangements in a transparent, commercial manner," U.S. National Security Council spokesman Gordon Johndroe told reporters at President George W. Bush's Texas ranch.

    "We urge both sides to keep in mind the humanitarian implications of any interruption of gas supply in the winter," Johndroe said.

    "The predictable flow of energy to Ukraine and the rest of Europe under market-based, transparent conditions is essential for stability and reliability in regional and global energy markets," the spokesman noted.

    Russia cut its natural gas supplies to Ukraine on Thursday morning after talks broke down over payments for past shipments and a new energy price contract for 2009.

    Ukraine is situated on the main transit route for Russian gas exports to Europe, with some 80 percent of the continent's gas supply from Russia crossing the Ukrainian territory.