UNITED NATIONS (AFP) - Chinese President Hu Jintao on Tuesday pledged to curb the growth of China's carbon dioxide emissions by a "notable margin" by 2020 from their 2005 levels.

But Hu also did not put a figure on the cuts, telling the UN General Assembly that the curbs would be measured by unit of Gross Domestic Product, in line with China's concerns about preserving its rapid economic growth.

"We will endeavor to cut carbon dioxide emissions per unit of GDP by a notable margin by 2020 from the 2005 level," Hu told a special summit on climate change.

China and other developing nations have long resisted mandatory emission curbs as part of the next treaty on fighting climate change.

Hu also pledged to "vigorously" develop renewable energy and nuclear energy.

Hu, whose speech had been billed by China in advance as a major statement on slow-moving climate negotiations, stood by developing nations' position that rich states needed to do more because of their historic responsibility for the problem.

Climate change "is an environmental issue but also, and more importantly, a development issue," Hu said.

"At stake in the fight against climate change are the common interests of the entire world," Hu said, stressing that the "vast number" of developing nations were affected.

"Developed countries should fulfill the task of emission reduction set in the Kyoto Protocol, continue to undertake substantial mid-term quantified emission reduction targets and support developing countries in countering climate change," Hu said.

Nations are due to meet in December in Copenhagen to lay the framework for the successor to the landmark Kyoto Protocol, whose obligations on wealthy nations to cut greenhouse gas emissions expire in 2012.

Developed nations, while pledging to fight global warming, have insisted that emerging powers also commit to action as part of Kyoto's successor.

Hu said that China, the world's third largest economy, "has made great achievements in development as shown in the profound changes in the livelihood of the people."

But he said that China "still lags behind more than 100 countries in terms of per capita GDP and it remains the biggest developing country in the world."