* U.N. chief met with Chinese president, premier
* U.N. to hold "largest ever" climate summit in September
* China wants rich nations to accept large emissions cuts (Adds Kerry, paragraph 14)
By Louis Charbonneau
UNITED NATIONS, July 29 China's leaders told U.N. Secretary-General Ban Ki-moon that Beijing wants to reach a new agreement on combating climate change in Copenhagen in December, Ban said on Wednesday.
"I was pleased that President Hu Jintao and Premier Wen Jiabao assured me that China wants to seal a deal in Copenhagen in December and that China will play an active and constructive role in the negotiations," Ban told a monthly news conference.
The U.N. chief returned on Tuesday from official visits to China and Mongolia at which climate change topped the agenda.
China recently passed the United States as the biggest emitter of greenhouse gases and together the two countries account for 42 percent of the world's emissions.
Greenhouse gas emissions are widely considered to be one of the principal causes of global warming. Nations will gather in Copenhagen in December to work out a new agreement on reducing emissions to succeed the current Kyoto Protocol, whose first phase ends in 2012.
Climate concerns are expected to be high on the agenda when U.S. President Barack Obama visits China for a summit meeting with Hu later this year.
They will also be the subject of a summit in September in New York on the sidelines of the annual General Assembly gathering of world leaders. Obama and Hu are both expected to attend, U.N. officials say.
'LESS THAN FIVE MONTHS' TO SEAL DEAL
Ban said more than 100 heads of state and government were planning to attend the September summit, intended to help build momentum before the Copenhagen conference.
He said it would be "the largest gathering of leaders on climate change ever."
"Two years ago, only a few leaders could speak to these issues," Ban said. "Today, leaders are walking the road to Copenhagen together. But we have less than five months to seal a deal."
The U.N. chief also said he would travel to the Arctic polar ice rim next month to get a first-hand look at conditions there -- above all, the melting sea ice.
Earlier on Wednesday, Xie Zhenhua, a deputy chief of China's National Development and Reform Commission, which steers climate change policy, told the official Xinhua agency that industrialized nations must agree to large, measurable cuts in their emissions if a deal is to be sealed in Copenhagen. [ID:nLT624148]
He was speaking after the United States and China signed an agreement that promises more cooperation on climate change, energy and the environment without setting firm goals. [ID:nN28530225]
In a speech in Washington, U.S. Democratic Senator John Kerry criticized the agreement, saying, "More could have been achieved." He said it lacked dates, timelines and "specific steps that need to be taken" ahead of Copenhagen.
Xie's comments stopped short of Beijing's insistence earlier this year that developed nations should make cuts in greenhouse gas output of "at least 40 percent" below 1990 levels by 2020, suggesting the world's top emitter may be softening its stance with an eye on reaching a pragmatic deal.
Industrialized nations say that steep, expensive cuts in emissions are out of reach when they are trying to stimulate recession-hit economies.
The key players in Copenhagen have been struggling to reach a consensus on other core issues like financing climate change adaptation programs in developing nations and the transfer of clean technology. (Additional reporting by Richard Cowan in Washington and Emma Graham-Harrison in Beijing; Editing by Peter Cooney)