Governments must do more to fight global warming, spurred by a new UN scientific report and damage to nature that is already as frightening as science fiction, UN Secretary-General Ban Ki-moon said yesterday.

"This report will be formally presented to the (UN Climate Change) Conference in Bali," Ban told delegates from more than 130 nations in Valencia and praised them for agreeing an authoritative guide to the risks of climate change on Friday.

"Already, it has set the stage for a real breakthrough - an agreement to launch negotiations for a comprehensive climate change deal that all nations can embrace," he said.

Ban singled out the United States and China, the world's top two emitters of greenhouse gases, which have no binding goals for curbs, as key countries in the process. He welcomed initiatives by both and urged them to do more.

"I look forward to seeing the US and China playing a more constructive role starting from the Bali conference," Ban told a news conference. "Both countries can lead in their own way."

Ban said he had just been to see ice shelves breaking up in Antarctica and the melting Torres del Paine glaciers in Chile. He also visited the Amazon rainforest, which he said was being "suffocated" by global warming.

"I come to you humbled after seeing some of the most precious treasures of our planet − treasures that are being threatened by humanity's own hand," he said.

"These scenes are as frightening as a science fiction movie," Ban said. "But they are even more terrifying, because they are real."