BEIJING, April 25 (Reuters) - Reports that China is on course to become the world's top emitter of greenhouse gases this year or next are "utter nonsense", a top Chinese climate change official was quoted on Wednesday as saying.

The International Energy Agency said last week that China would overtake the United States as the world's biggest emitter of heat-trapping carbon dioxide either this year or next, confirming an earlier Reuters report.

Gao Guangsheng, head of China's Office of the National Coordination Committee for Climate Change, said the claim did not have a concrete statistical basis.

"For some international organisations to reach the conclusion that China's carbon dioxide emissions are about to surpass the United States' is not only irresponsible but is also being used to apply pressure on the Chinese government," the Oriental Morning Post quoted him as saying.

The most recent official inventory of China's emissions was from 1994, Gao added, and "at that time they were far lower than U.S. levels". He did not give any estimate of Chinese emissions.

But since then, China has notched up well over a decade of double-digit annual growth and as the economy booms, so does energy consumption -- the majority of it provided by carbon intensive and dirty-burning coal.

Chinese officials had previously said they could not comment on the Reuters report that China could be the top emitter this year because they did not have accurate data on their own emissions.

China has delayed the launch of a national climate plan, originally due to be unveiled on Tuesday, while officials tweak details, sources said.

The country's first national assessment of the challenges posed by global warming suggests aiming to nearly halve by 2020 the amount of greenhouse gases it emits for each dollar of its economy, but says China should reject strict caps for decades in order to safeguard economic development.

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