The US government has urged Russia to immediately restore gas supply via Ukraine to the European Union (EU).
"The US welcomes the agreement brokered by the Czech presidency of the EU to enable the restoration of gas flows to European customers and provide greater transparency along the transit route," State Department spokesman Sean McCormack said on Monday.
"Now that this agreement is in place, we call upon Russia to restore gas flows immediately. We also urge Russia and Ukraine to conclude quickly a deal on the sale and transit of gas," he added.
On Sunday, Czech Prime Minister Mirek Topolanek brokered an agreement between Russia, the EU and Ukraine to create a mechanism to monitor Russian gas delivery to Europe through Ukraine.
According to the monitoring deal, EU representatives and energy officials from Russia and Ukraine would be allowed to travel to gas pumping stations on Ukraine's eastern and western borders to track gas flow.
Russia cut supplies to Ukraine Jan 1 over a dispute regarding gas prices and overdue payment, and subsequently shut down gas flows intended for Europe via Ukraine, causing supply shortages in at least 18 countries.
About 80 percent of Russian gas to Europe is shipped via Ukraine.
"This incident once again underscores the importance of diversifying supplies of natural gas and of transparent, market-oriented arrangements for the sale and shipment of natural gas," McCormack said.
A similar dispute resulted in a briefly interrupted delivery of Russian gas to many European countries in January 2006.
Russia's Prime Minister Vladimir Putin has told Topolanek that gas shipments to Europe via Ukraine will be resumed as soon as the monitoring mechanism starts functioning.
Russia's state-owned energy giant Gazprom and Ukraine's Naftogaz have not reached a compromise yet on the gas debts owned by Ukraine or for a new contract between the two in 2009.