World leaders have reached a deal to fight climate change on Friday after tense negotiations in Copenhagen, Chinese sources in the talks said.

There will be a closing ceremony of the UN climate change conference around midnight, the sources said. The Chinese premier's delegation is leaving Copenhagen for home after two days of talks.

Earlier, U.S. President Barack Obama said a "meaningful and unprecedented breakthrough" had been achieved on the deal.

But Obama said the agreement, sealed after long hours of tense negotiations among world leaders, is not legally binding and was still under drafting. "It is going to be very hard, and it is going to take some time" to get to a legally binding treaty, he said.