"To have a figure put on an American undertaking, announced by the White House, is worthwhile progress," said environment minister Jean-Louis Borloo as he set off for Beijing for talks with Chinese officials.

World leaders will meet in the Danish capital for 12 days from December 7 to try to agree a global pact to reduce manmade emissions of the gases that are blamed for climate change.

Campaigners have branded the summit the world's last chance to halt or slow global warming before catastrophic damage is done to the environment, but US President Barack Obama has been trying to moderate expectations.

Borloo admitted that the US administrations 17 percent offer falls well short of the kind of cuts that most climate scientists agree are necessary, but said: "It's an extremely encouraging first response."

But he regretted that Obama plans to attend an early session of the summit, on December 9, and not the conclusion more than a week later when other heads of state will be in Copenhagen hoping to sign a binding treaty.

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