UK's Stern sees good chance for deal in Copenhagen

* Climate expert Stern sees political deal, not full treaty

* Sees U.S. as biggest obstacle, but notes 'progress'

* Urges U.S. to boost climate aid to developing nations

By Dave Graham

BERLIN, Nov 4 (Reuters) - World powers have a "very good chance" of reaching a political deal to target global curbs in carbon emissons at a U.N. conference in Copenhagen next month, British climate change expert Nicholas Stern said on Wednesday.

Stern, author of an influential 2006 report for the British government on the impact of global warming, said he did not expect a "formal treaty" to be signed in Copenhagen, partly due to resistance in the United States.

"But we can and should put together a strong and clear political deal. I think that a complete failure in Copenhagen would be very damaging. But I don't think that will happen.

"I think so many people want it to succeed that we've got a very good chance," Stern told a news conference before delivering a lecture at Berlin's Technical University.