China yesterday confirmed that it will demand rich nations cut greenhouse gas emissions by 40 per cent from 1990 levels by 2020 in upcoming global climate change negotiations.

In a position paper published for negotiations to be held in Copenhagen in December, China - one of the world's largest emitters of greenhouse gases that cause global warming - did not commit to any legally binding reductions.

"Developed countries shall undertake to reduce their GHG (greenhouse gas) emissions in aggregate by at least 40 per cent below their 1990 level by 2020," said the paper, posted on China's planning agency's website.

"Developed countries shall take responsibility for their historical cumulative emissions and current high per capita emissions to change their unsustainable way of life and to substantially reduce their emissions."

The call for a 40 per cent cut by rich countries has previously been mentioned in state media, but yesterday's document spells out the demand as official Chinese government policy.

The December negotiations are aimed at hammering out a new climate change pact to replace the Kyoto protocol that expires in 2012.

The European Union has said it would slash emissions by 20 per cent by 2020 compared with the 1990 level and raise the target to 30 per cent if others set similarly ambitious targets.

State press reports earlier said China was prepared to commit to improved energy efficiency as its contribution to the talks, but such targets were not set out in the position paper.