China's chief climate change negotiator, two days into the two-week conference, voiced his frustration over Japan's forceful rejection of an extension to the gas restrictions set under the Kyoto Protocol, calling the decision "not a very welcomed position".

Su Wei, head of the climate change department of China's National Development and Reform Commission, also called on all participating countries to work together. Otherwise, he said, "we all draw back".

"The (Kyoto Protocol) is a very important conventional tool to help achieve optimistic objectives in climate change," he said.

Earlier on Tuesday, Kuni Shimada, the special adviser to Japan's environment minister, rejected any extension of the treaty's gas restrictions beyond 2012 and said "Japan will not inscribe its target under the (Kyoto Protocol) on any conditions or under any circumstances".

The decision has already cast a pall over the conference.

The Kyoto Protocol is the pillar and one of the most critical elements for success in Cancun and discontinuation of the treaty will be a disaster, Su said. It is the first global agreement with mandatory restrictions on greenhouse gases.

Many developing countries receive significant emissions credits because of the treaty.

Su, like many Chinese officials, said that the nation is ready to make its contributions toward fighting climate change.

China expects a continuation and commitment to the treaty. Beijing also expects developed nations to transfer clean-energy technology and offer financial support, Su said.

He added that China has held many discussions with other countries including the US to move the process forward.

"I don't think we have much contention (with the US) as seen by the media and outside," he said.

He added that China doesn't see a problem in increasing transparency and providing information with other countries about its methods in tackling climate change. China has set what Su called a "scientific assessment system" to evaluate actions aimed at achieving its carbon reduction targets.

As the second largest economy, China has been called on to shoulder more responsibilities. But Su reminded the media that it would be a different story when China's population is divided by 1.3 billion with 140 million living in serious poverty, he said.

"It's very clear that China is still a developing country, in terms of per capita GDP, we are just one-tenth of the US. How could we be a developed country?" Su said.

In terms of per capita, China isn't the biggest emitter, Su said. The US is still the world's biggest emitter as well as the largest emitter in terms of per capita.

China's greenhouse emissions per person are approximately one-quarter of the US', said Martin Khor, executive director of the South Center, who said he got the figure from a group of scientists. Khor also said that China's per person historical contribution to climate change is less than 7 percent of the US.

The current climate change issue is caused by the accumulation of developed countries in their 200 years of industrialization. Su said that developing countries also have obligations to address the climate change issue

"Everybody should do its fair share to solve the issue," he said. "We recognize the US is doing a lot over issues of climate change especially since President Barack Obama took office."