"The EU today said, 'yes, we can and here's how,' and that's pretty good," Kerry told AFP as ministers prepared to wrap up 12 days of talks in Poznan, Poland on preparing a global climate pact to be signed in Copenhagen next December.

The pact is "very exciting," he said.

"It represents an enormous act of leadership which will have an impact on Poznan, it will have an impact on Copenhagen," Kerry said.

"I think it shows an example of what is possible if you work hard and come up with details for how you can reduce emissions and help countries that have different economies and different needs."

He added: "So that's our challenge. It's really to do things on a global scale and I think this example will have an impact."

EU leaders, on the final day of a Brussels summit, ironed out deep differences to approve the most ambitious climate package of any economic power.

The European Union was credited with saving from oblivion the Kyoto Protocol on reducing rich countries' carbon emissions after outgoing US President George W. Bush refused to ratify it in 2001.

The 27-nation bloc's pact, setting down curbs in greenhouse-gas emissions by 2020, was a key test of whether it would continue to lead the way or flail in the face of the world's financial crisis.

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