The United States on Thursday urged the restoration of normal gas deliveries after Russia cut off supplies to Ukraine over a contract dispute, and asked both sides to consider the humanitarian implications of any interruption during winter.

"The United States would like to see a restoration of normal deliveries. The parties should be resolving their differences through good-faith negotiations, without supply cutoffs," White House spokesman Gordon Johndroe said in a written statement from Texas where President George W. Bush is on vacation at his Crawford ranch.

Russian gas export monopoly Gazprom halted supplies to Ukraine on Thursday morning after a failure to agree on terms for 2009.

"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," Johndroe said.

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

Ukraine's Naftogaz said it had seen a reduction of pressure in its pipelines, and was pumping gas from its reserves. Gazprom said it had increased deliveries for export to European consumers beyond Ukraine.

Pipelines that cross Ukraine carry about one-fifth of the European Union's gas needs. Both Russia and Ukraine say they will not jeopardize supplies to Europe.

"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," Johndroe said.