SHANGHAI, Apr 24 (AP) -- China will overtake the United States as the world's biggest source of greenhouse gasses this year, a news report cited the International Energy Agency as saying.

China had been forecast to surpass the U.S. in 2010, but its sizzling economic growth has pushed the date forward, IEA chief economist Fatih Birol was quoted as saying in an interview in Tuesday's Wall Street Journal newspaper.

"In the past couple of months, economic growth and related coal consumption has grown at such an unexpected rate," Birol was quoted as saying. China's rising emissions will effectively cancel out other countries' attempts to reduce their own, he said.

The comments follow the release over the weekend of a Chinese government report detailing the costs of climate change, but asserting that the country should focus on development before cutting greenhouse gas emissions.

It said emission limits were unfair and would constrain China's current energy and manufacturing industries.

Higher-than-average temperatures mean spreading deserts, worsening droughts, shrinking glaciers and increased spread of diseases, said the report, compiled by more than a dozen government bodies.

China is a signatory to the Kyoto Protocol on reducing greenhouse gasses, but it is exempt from its restrictions because it is a developing country.

The Paris-based International Energy Agency advises developed countries on energy policy.