"Today marks the point when the political momentum has shifted in favor of a seeing a fair, effective and ambitious climate deal in Copenhagen," the UN secretary general said at the end of day-long talks by 100 heads of state.

"There is still a long way to go but today we are closer to a deal. We need to maintain this momentum in the coming weeks leading into Copenhagen."

Ban convened the talks to push nations towards publicly committing themselves to seal a new climate deal at the talks in the Danish capital to succeed the landmark Kyoto Protocol which expires in 2012.

Ban pointed to the pledges by Japan's new Prime Minister Yukio Hatoyama, who wants cuts in carbon emissions of 25 percent by 2020 from 1990 levels, compared with the previous conservative government's eight percent target.

"That is a quantum jump. I think the Japanese government's ambitious target will change some dynamics among some of the countries," Ban said.

Chinese President Hu Jintao, meanwhile, told the conference that the emerging power was ready to slow down the intensity of carbon emissions in its rapid economic growth. Hu said China would shift increasingly to green technology and embark on a tree-planting initiative.

"I think that anyone who still doubts their sincerity on climate change needs to take another look. China realizes the impact that climate change has and that they must act," Ban said.

Danish Prime Minister Lars Loekke Rasmussen, the host of the make-or-break talks in Copenhagen, acknowledged that gaps remained but also voiced optimism.

"It's not as simple as it sounds but it's doable," Rasmussen said of a climate deal in Copenhagen.

"After today's meeting, I am very encouraged that we will get there and seal the deal in Copenhagen on December 18," he said.

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