A high-ranking United Nations official said China's decision to make a 40 to 45 percent cut in carbon intensity by 2020 is "a milestone" leading up to the Copenhagen summit, which opens Dec 7.

On Friday, UN Development Program (UNDP) administrator Helen Clark downplayed the potential of the Copenhagen summit, predicting that leaders will have a tough time reaching a global alliance next month.

She urged closer cooperation in mitigating climate change between China and the UN in a speech she made in Beijing on Friday at the 30th anniversary celebration of her organization's presence in China.