President Hu Jintao is upbeat about the prospects for a positive outcome at the Copenhagen climate change summit in December - as long as the international community collaborates based on agreed principles and achievements made so far.

"It is essential that any result from the conference should embody the basic principles of the UN Framework Convention on Climate Change and the Kyoto Protocol and lock in the achievements of the Bali Roadmap," Hu said yesterday.

He was referring to an action plan agreed at the UN climate talks in December 2007 that kicked off the negotiations aimed at finding a broader agreement capable of expanding or replacing the Kyoto Protocol after it expires in 2012. That process is meant to conclude in Copenhagen.

During the conversation, which was aimed at breaking the deadlock in international climate negotiations, the leaders agreed to extend collaboration on tackling global warming between the world's two biggest greenhouse gas emitters.

"Developing cooperation between the two sides on climate change issues would not only benefit the international community in its efforts to tackle climate change, but also have great significance for promoting the development of China-US ties," Xinhua News Agency quoted Hu as saying.

Hu added that "the two nations face common challenges in tackling climate change and share common interests".

Obama said both the US and China had taken important steps in dealing with climate change, and he said the two should push for concrete and meaningful steps to meet the challenges and make the Copenhagen conference a success.

The leaders met at the UN climate change summit in New York in September, during which Hu pledged that China will "notably cut" carbon intensity by 2020. Hu did not set a specific goal at that time.

There is a good deal of speculation that the two nations will reach a bilateral climate change agreement before the Copenhagen conference begins.

Analysts said any deal at Copenhagen will need to have the full support of the world's two largest emitters.

"China and the US must coordinate and reach a concrete and practical solution acceptable to both countries that can be brought to Copenhagen," said Zhou Qi, a senior US expert with the Chinese Academy of Social Sciences. "Both sides have to make compromises."

There has been growing concern recently among politicians and the public around the world that the UN climate talks on expanding the fight against global warming have largely stalled, making the outcome of the Copenhagen summit uncertain.

The last round of climate talks, which was held in Bangkok between Sept 28 and Oct 9, resulted in progress toward a draft text for a likely agreement but failed to break the deadlock in key areas.

Developed countries have been calling on emerging nations - including China and India - to commit to reduce carbon emissions.

However, developing countries have insisted that they will not agree to reductions without a transfer of finances and technology from rich nations.

Yuan Peng, head of the Institute of US Studies, affiliated to the China Institute of Contemporary International Relations, said a compromise calls for the US to agree to the technology transfer while China must agree to a detailed carbon reduction target.

"The US has to accept that China, as a developing nation, is not in the position to commit to a binding emission reduction target," said Zhou.

Washington senator Maria Cantwell said early last month that the US and China are likely to sign an agreement to combat climate change during Obama's visit to Beijing in November.

Cantwell said a deal between the two nations would help build global confidence in the fight against global warming.

Xinhua, Reuters contributed to the story