Teams of EU monitors traveled to gas pumping stations Sunday along Ukraine's extensive pipeline network, as Russia prepared to resume natural-gas shipments through Ukraine to Europe.
Ukraine signed a deal early Sunday to allow European, Russian and its own experts to track the flow of Russian gas through Ukraine pipelines. The Kremlin insisted on a written agreement on the multinational monitoring mission before it would restart gas flows.
Russia's state gas giant Gazprom cut off all supplies to Europe on Wednesday amid an acrimonious dispute over prices, deliveries and debts with Ukraine.
The cutoff came at a time of diplomatic tensions between the two countries, following Ukraine's efforts to join NATO and its support for the former Soviet republic of Georgia in its war with Russia in August. Both moves have brought bitter criticism of Kiev from Moscow.
Ukrainian officials say it might take up to three days for gas to reach European countries.
Russian Prime Minister Vladimir Putin promised that Moscow would resume gas shipments through Ukraine once the deal is signed and monitors are in place.
Russia demanded the monitors, saying it was the only way to prevent Ukraine from stealing Russian gas intended for Europe. Ukraine hotly denied the accusation, saying Russia was not providing enough gas to pump the rest of the gas west to Europe.
The European Union is urging Russia and Ukraine to restart pumping natural gas to Europe immediately. The EU's executive commission said Sunday there was no reason to further delay gas supplies because EU monitors are now in place to check that no gas is siphoned off.
EU monitors have arrived at Russia's Sudzha station and at Lugansk in southeastern Ukraine. They are also heading to sites in western Ukraine at Orlovka, Uzhgorod and Drozdowichi. Monitors will also be in Kiev and Moscow.
Czech Prime Minister Mirek Topolanek, whose country holds the rotating EU presidency, shuttled between Moscow and Kiev on Saturday to mediate the deal. He finally persuaded Ukraine to accept the monitoring pact during marathon talks that dragged into early Sunday.
"Nothing prevents Russia now from resuming gas supplies," Topolanek said.
"We once again have shown our goodwill," Ukrainian Prime Minister Yulia Tymoshenko said, adding that the mission would show Ukraine to be an "honest transit country."
Bohdan Sokolovsky, an energy adviser to the Ukrainian president, told The Associated Press it would take Russia about 30 hours to start the flow of gas, and then it would take an additional 36 hours for Ukraine to pump the gas to its western borders.
Russia supplies about one-quarter of the EU's natural gas, 80 percent of it shipped through Ukraine, and the disruption has come as the continent was gripped by subfreezing temperatures. At least 11 people have frozen to death this week in Europe, including 10 in Poland, where temperatures have sunk to minus 25 C.
EU governments have criticized both Russia and Ukraine for the energy crisis.
US National Security adviser Stephen Hadley warned Russia that using its energy exports to threaten its neighbors would undermine its international standing.
The Russian state natural-gas giant Gazprom halted the shipment of the gas it supplies to Ukraine on January 1 after negotiations broke down over a 2009 contracts.
But Gazprom kept pumping gas to central and western Europe through Ukraine. Ukraine's 37,800 kilometers of pipeline - one of the largest gas pipeline systems in the world - handles both Ukraine's domestic gas and gas for export.
Both Russia and Ukraine have been hard hit by the global economic slowdown. Energy is the driving force behind Russia's economy, and the fall in oil prices in recent months has hit Moscow hard.
Ukraine, meanwhile, faces economic collapse and is desperate to avoid higher gas prices.
A 2007 report by the Oxford Institute of Energy Studies called Ukraine "the most energy-intensive economy in the world," consuming about 73 billion cubic meters of gas in 2005, roughly that used by all of Africa.
Last year, Russia charged Ukraine $179.50 per 1,000 cubic meters, about half what it charged its European customers. Ukraine's Naftogaz company chief Oleh Dubyna said the latest round of talks on the 2009 gas contract ended Saturday without result, with Gazprom demanding a price of $450.