China keen to see CO2 emissions peak: diplomat

"I try to remain an optimist because the nature of the problem is such that we cannot afford a failure."

Asked whether China had abandoned a demand for a 40 percent cut in rich nation emissions by 2020, Yu said that a target for developed countries should be agreed in the talks.

"As the developed countries have a historical responsibility for climate change, they should continue to implement large emissions cuts after 2012," Yu said.

"A concrete figure has to be decided by the negotiations; we will get a result in Copenhagen," he said, but added Beijing still considered the 40 percent sought by developing countries in previous talks a "fair and rational" target.

He slammed rich nations for trying to escape obligations agreed under previous climate deals, or force excessive commitments from poorer countries.

Yu also defied critics who say Beijing is throwing up coal-fired power stations at a terrifying rate, and has little real interest in environmental concerns.

He pointed to a massive efficiency drive that is gathering speed after a slow start, and a push to make renewables 15 percent of the country's energy mix by 2020.

"Among all countries in the world, China is probably doing best in terms of achievements in reducing carbon emissions."

(Editing by David Fogarty)