(AP) -- The top U.S. negotiator on climate change said Tuesday that he is slightly more optimistic about striking a new international agreement to curb global warming after a two-day meeting with the world's largest emitters of greenhouse gases.
Todd Stern, the U.S. special envoy for climate change, told reporters at a briefing Tuesday that he is "a bit more optimistic" that the U.S. will be able to broker a new deal in Copenhagen in December.
But he warned that it is not going to be easy, since many of the potential sticking points for a new global pact still need to be worked out.
"I walk away more optimistic," Stern said at the conclusion of the Major Economies Forum on Energy and Climate. "It does not change the fact that the issues are extremely difficult, that it is not going to be easy to reach agreement, or we wouldn't be doing this."
The Washington meeting is the first of a series of three called for by President Barack Obama. The goal is to help broker a replacement to the 1997 Kyoto Protocol, the international climate treaty that expires in 2012, and to build support for the development of pollution-reducing technologies.
The U.S. never signed onto Kyoto, citing the costs to the economy and the lack of participation by developing countries like India and China.
Those two issues continue to loom over negotiations more than a decade later. But the Obama administration has said it is committed to overcoming them in order to reach a deal.
At the two-day meeting, the administration showed participants it was serious.
Representatives of the 16 major economies present heard presentations from a host of top-level officials, including Secretary of State Hillary Rodham Clinton, Energy Secretary Steven Chu and White House science adviser John Holdren. Together with the United States, the represented countries account for 80 percent of the global emissions of heat-trapping gases.
Late Monday afternoon they attended a reception at the White House with Obama.
"We come out of it more encouraged about the commitment of all the participants, particularly the United States," said Joao Vale de Almeida, the head of the European Union delegation. "The most important change as we started this meeting was of course the position of the United States. This means the U.S. is fully back in the debate and because of that we are back in business in terms of finding a global solution to a global challenge."
But behind the scenes, two key issues still pose challenges: how much rich countries will pledge to reduce climate-changing pollution and how to raise an estimated $100 billion a year to help poor countries adapt to climate change.
The Obama administration has called for a 14 percent to 15 percent reduction in greenhouse gas emissions from 2005 levels by 2020 and legislation before Congress would reduce such emissions by 20 percent by 2020. Developing countries and the European Union are pressing the U.S. to make deeper cuts.
Stern said these were the two numbers on the table for the U.S.
"What I said to the delegates is that you effectively got a United States number there. It is somewhere in that range," Stern said.
But Yvo de Boer, head of the United Nations climate change secretariat, said that even the reductions being talked about by industrialized nations aren't enough to avoid rising sea levels, harsher storms and droughts. That would require a 25 percent to 40 percent reduction in global emissions.
"It wasn't all sweetness," de Boer said. "Those numbers are still very far from what the scientific community tells us" needs to be done.
The meeting never got around to addressing the financing issue. They ran out of time.
The next meeting is scheduled for May in Paris.
Associated Press writer Natasha T. Metzler contributed to this report.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: US delays decision on Keystone pipeline project