Todd Stern said Washington wanted major economies including China, the European Union and Russia to seek more common ground on issues such as green technology, finance and emissions cuts at talks in Paris on May 25-26.
The talks are the second among major nations accounting for about 80% of world greenhouse gas emissions under a plan by US President Barack Obama to contribute to a new UN climate pact due to be agreed in Copenhagen in December.
Stern told Reuters that many nations viewed the meetings as "a place where actual progress may be made on issues that otherwise would hang up the (UN) negotiations".
But Stern, who is US Special Envoy for Climate Change, said the US-run Major Economies Forum (MEF) would not necessarily seek to culminate in July with agreement on firm greenhouse gas targets and dates.
"It may be that we have some numbers [...] in July. The honest answer is that I don't know yet," he said in a telephone interview. A MEF summit is due on the margins of a summit of the Group of Eight industrial nations in Italy in July.
Paris is the second preparatory ministerial meeting after one in Washington in April. A third is due in Mexico in June.
Asked if Washington might try to get MEF nations to agree to harden a "vision" of halving world greenhouse gas emissions by 2050 agreed by a G8 summit in Japan last year, Stern said:
"I don't think it's necessarily a question of thinking about this all in terms of whether there will be a 2050 (target) as much as 'are countries going to move towards agreeing a set of principles of the kind that will advance the ball in Copenhagen?'
Droughts, floods
The UN talks comprise almost 200 nations, aiming for a deal to rein in warming that the U.N. Climate Panel says will cause more droughts, floods, crop failures, spread disease and raise sea levels.
The Paris talks will group Australia, Brazil, Britain, Canada, China, the European Union, France, Germany, India, Indonesia, Italy, Japan, South Korea, Mexico, Russia, South Africa and the United States. Denmark as host of the Copenhagen meeting and the United Nations are also invited.
Obama has promised to cut US emissions to 1990 levels by 2020, a cut of about 14% from 2007 levels. Many developing nations, led by China and India, say the rich should make far deeper cuts.
Stern also said he was not worried that a bill under consideration by the House Energy and Commerce Committee would water down Obama's goal of auctioning 100% of permits to emit carbon dioxide to industries.
Under the draft sponsored by Representatives Henry Waxman and Edward Markey, about 85% of permits would initially be given away free to industries as part of a system to cap U.S. emissions and allow a carbon trading market.
"I'm actually not worried about that at all," Stern said of the free allowances. "The Waxman bill still has a long road to go. The road ahead will not be easy."
"The issue of having 100% auctions is a great policy idea but we are always in the realm of the art of the possible," he said. "A cap is a cap. If it binds it binds. If some emissions go over some period of time to compensate people or companies who are hard hit I think that's part of the process."
(EurActiv with Reuters.)
