Representatives of the world's 17 biggest and most polluting nations held talks Sunday to search for a breakthrough on financing efforts to contain climate change and reduce gas emissions causing global warming. Pressure has been mounting for 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. "With only 50 more days to go before the final talks at Copenhagen, we have to up our game," British Environment Minister Ed Miliband said in a statement released Sunday. "Britain is determined to throw everything at this because the stakes are so high." Earlier, Miliband had said it was "important that the US makes as much progress as possible" at the two-day meeting of the Major Economies Forum. The Obama administration said it was tied to action by Congress, where climate bills were making their slow way toward legislation - an argument that cut little ice with other negotiators. "The rich countries of the Major Economies Forum must urgently put new money on the table to ensure the developing world can grow cleanly and adapt to the effects of climate change, which are already putting millions of lives at risk," said Asad Rehman of Friends of the Earth. Miliband said there had been some progress, pointing to recent commitments by Japan and China aimed at reducing emissions. "There are some good straws in the wind, but there are also some big obstacles to overcome," Miliband told the BBC. He insisted that the meeting in London could tackle differences between developed and developing nations outside the formal UN negotiating process. "The truth is if this is left to the negotiators... I think we'll fail," Miliband said. "If we can get a way forward, narrow some of the differences between the countries which represent the lion's share of the problem, then it might make those UN talks a bit easier." Swedish Environment Minister Andreas Carlgren, representing the European Union, will hold separate talks with representatives from China and India during the meeting, his spokesman said. One further negotiating session is set for November in Barcelona. But pessimism was mounting that a deal could 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 UN scientific panel studying climate change, wrote Friday Newsweek's Web site. 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 to develop their economies without overly increasing pollution. Estimates range in the hundreds of billions of dollars needed every year, but a formula for raising, administering and distributing the funds has proved elusive. Rapidly growing nations such as 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 scientists say are required to avert climate catastrophes.