(AP) -- The world's 17 biggest and most polluting nations meet in London on Sunday in an attempt to break a deadlock on financing efforts to contain climate change and reducing harmful gases causing global warming.
With a deadline looming, pressure was mounting on the United States to finalize its position before a decisive December conference in Denmark meant to cap two years of negotiations on a global climate change treaty.
International negotiators showed little patience with arguments from the Obama administration that it was tied to action by Congress, where climate bills were making their slow way toward legislation.
"It's important that the U.S. makes as much progress as possible. They must come to Copenhagen with a clear sense of what they want to do," British Environment Minister Ed Miliband told British reporters in advance of the meeting.
Negotiators working on a bulky text of an agreement will meet for the last time before the December conference in early November in Barcelona, Spain.
But pessimism was mounting that a deal can be struck without policy changes at the highest level.
"In recent months, the prospects that states will actually agree to anything in Copenhagen are starting to look worse and worse," Rajendra Pachauri, head of the authoritative U.N. scientific panel studying climate change, wrote on the Newsweek Web site posted Friday.
President Barack Obama initiated the Major Economies Forum earlier this year as an informal caucus to quietly deal with the toughest problems. Participants agree to keep the talks confidential.
A key issue is helping poor countries adapt to changes in the earth's climate that threaten to flood coastal regions, make farming unpredictable and spread diseases. They also need funds and technologies allowing them to continue develop their economies without overly increasing pollution.
Estimates range in the hundreds of billions of dollars needed annually, but negotiators were struggling to find a formula for raising, administering and distributing the funds.
Rapidly growing nations like India, China, Brazil and Mexico have agreed to draw up national strategies for slowing the growth of greenhouse gas emissions, but resist making those limits binding and subject to international monitoring in a treaty.
Industrial countries agree to reduce their own emissions, but not to the levels that scientists say are required to avert climate catastrophes.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Oil globs close Los Angeles-area beaches to swimming (Update)