MOSCOW, Jan. 2 - Faced with mounting criticism from its natural gas customers across Western Europe, Russia on Monday restored most of the gas it withheld from Ukraine's pipeline system a day earlier in a pricing dispute.

Officials of the state-owned Russian company, Gazprom, presented the decision not as a reversal but as a response to Ukraine's "theft" of natural gas. But it became clear almost immediately that the driving force in Russia's decision was the sharp criticism across Europe, including countries like Germany that are usually reliable allies.

Just hours after Russia disrupted gas supplies on Sunday morning by reducing pressure in the pipeline system, a cascading energy emergency moved westward across Europe, as one utility after another reported dropping gas pressures -- at a time of peak demand in freezing weather.

As pressure continued to drop Monday, criticism erupted among European leaders, jittery over the threat to one of the Continent's primary sources of energy. The minister of economy in Germany, the largest consumer of Russian natural gas in Europe, questioned Russia's reliability as an energy supplier.