(Wall Street Journal Asia) - China's government disputed the International Energy Agency's assertion that China surpassed the U.S. as the world's largest energy consumer last year, highlighting the lack of clarity in China's energy sector as well as the country's unease at its growing global impact.

"By our calculation, the U.S. was still the world's largest energy user in 2009," said Zeng Yachuan, a spokesman with China's National Energy Administration. Zhou Xi'an, a director with the agency, told reporters that "the IEA data can be used as a reference but are not very reliable."

The IEA said that last year China used 2.252 billion tons of oil equivalent, a measure of energy including oil, gas, coal, uranium and all other sources. That figure is about 4% more than the U.S., which the IEA said burned 2.17 billion tons of oil equivalent. On a per capita basis, Chinese energy demand is still around a third of the average of industrialized nations, according to IEA data.

The IEA quickly defended its analysis Tuesday. "All the relevant sources of statistics indicate that China has surpassed the United States to become the world's largest energy consumer," IEA chief economist Fatih Birol said.

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