UN Secretary-General Ban Ki-moon on Thursday spoke highly of China's "very important role" in addressing the global challenge of climate change.

Ban made the remarks in an interview with UN-based Chinese journalists before traveling to Copenhagen, Denmark, to push for a global deal on climate change.

The UN Climate Change Conference, which opened Monday and will run through Dec. 18, gathered representatives from 192 countries with the aim to map out a plan to combat climate change over the period of 2012-2020.

"The recent announcement by China to reduce energy intensity by 40 to 45 percent against the level of 2005 was very much appreciated," said Ban.

Recalling a visit to China earlier this year, Ban said he was impressed by the "way the Chinese government and indigenous communities are doing to reduce greenhouse emissions by developing renewable sources of energy, by developing alternate sources of energy."

"Just by changing lightbulbs in the amount of 4 billion lightbulbs, China is going to reduce energy dependency by 7 or 8 percent," he said. "That is quite remarkable."

"I visited all those solar factories. That was very impressive," he said.

Introducing renewable sources and alternative sources of energy will be "extremely important" for addressing climate change, said the UN secretary-general.

Turning to the ongoing UN climate change conference in Copenhagen, Ban again voiced optimism about "a robust, strong political agreement" which will include all four important elements.

"That is the ambitious emissions mid-term targets by developed countries as recommended by the intergovernmental panel on climate change, that means a 25 to 40 percent reduction of greenhouse emissions," he said.

"And developing countries should also take nationally appropriate mitigation actions, and a strong adaptation package for developing countries and financial and technological support for developing countries, particularly for the most vulnerable countries, and finally, a global governing framework should be agreed upon," he said.

The secretary-general regretted that there was still "a gap of trust" between developing and developed countries.

"One of the best ways to bridge this gap would be that industrialized countries should come out with sufficient financial and technological support," he said.

Ban said he would also make his best efforts to help bridge this gap, in a way that is "absolutely impartial."

"I will try to play a very fair and impartial role as an honest broker to bridge the gap between developed and developing countries," he said.

He underscored the principle of "common but differentiated responsibilities", which is the basis of negotiations.

"That's firm. That is agreed by all. There is no change," he stressed.

"I am basically optimistic about the result of Copenhagen because all the leaders believe that we do not have time and the science has made it quite clear that climate change is happening much, much faster than we realized," he said.

"We must deliver this planet Earth to our succeeding generations in a more environmentally sustainable way. That is our political and moral responsibility, and that's the responsibility of world leaders," he added.