"Because we're a coal dominant country, we have to take responsibility for lowering greenhouse emissions," Zhang Guobao, vice-chairman of the energy-policy setting National Development and Reform Commission, told an energy conference in Australia.

But Beijing would need to trim economic growth and hit energy efficiency targets to achieve a reduction, Zhang said.

"China plans to reduce its energy consumption per unit of GDP by 20 percent by 2010," he said.

"And for the next five years, assuming an average economic growth of 7.5 percent per year, China's carbon emissions will be reduced by 10 percent," he added, without specifying whether that would be per unit of national output.

The rare mention of a global warming target by a senior Chinese official comes barely a month after the International Energy Agency (IEA) warned that China's carbon emissions could overtake those of the United States before 2010.

China has much scope to improve its energy efficiency given that its energy consumption per unit of output far exceeds the United States and Japan, said Zhang, but its rapid economic growth means its gross carbon emissions could rise regardless.

Beijing has been heavily promoting its energy efficiency goals, but diplomats and analysts say this is largely because of domestic pollution problems and energy security concerns as dependence on oil imports creeps towards 50 percent.

Global warming is rarely mentioned as a priority by China's top leaders and carbon dioxide emissions are not targeted in the blue-print five-year plan for growth to 2010, despite lobbying from both inside and outside the government.

But Beijing has pledged to change its energy supply structure, including investments in cleaner coal, nuclear power and renewables.

Officials aim to boost the portion of its energy that comes from renewable sources to 16 percent of total supply from the current 7 percent by 2020.