| CANCUN, Mexico
CANCUN, Mexico Washington claimed progress in easing rifts with Beijing on ways to fight global warming on Monday as U.N. climate talks got under way in Mexico with warnings about the rising costs of inaction.
The United States and China, the world's largest economies and top greenhouse gas emitters, have accused each other of doing little to combat global warming in 2010, contributing to deadlock in the U.N. talks among almost 200 nations.
"I think that a success here will only emerge if we can both come to agreement," said Jonathan Pershing, heading the U.S. delegation at the talks in Cancun.
"We have spent a lot of energy in the past month working on those issues where we disagree and trying to resolve them. My sense is that we have made progress. It remains to be seen how this meeting comes out," he said.
The talks, in a tightly guarded hotel complex by the Caribbean with warships visible off the coast, are seeking ways to revive negotiations after the U.N. Copenhagen summit failed to agree to a binding treaty in 2009.
The United Nations wants agreement on a new "green fund" to help developing nations as well as ways to preserve rainforests and to help the poor adapt to climbing temperatures. It will also seek to formalize existing targets to curb greenhouse gas emissions.
China's chief delegate, Su Wei, was more guarded about progress.
"We've had a very candid, very open dialogue with our U.S. friends and I think both the U.S. and China would very much like to see a good outcome at Cancun," he told Reuters.
Climate is one of several issues dividing the two as well as disputes over trade and exchange rates. Preparatory U.N. climate talks in China in October were dominated by disputes between Washington and China.
Pershing also said President Barack Obama was committed to a goal of cutting U.S. greenhouse gas emissions by 17 percent from 2005 levels by 2020 despite Republican gains in mid-term elections.
Earlier, the talks opened with calls for action to avoid rising damage from floods, droughts, heatwaves and rising sea levels.
"Our relation with nature is reaching a critical point," Mexican President Felipe Calderon said.
"Delays in action would only lead to impacts which would be much larger and in all likelihood more severe than we have had so far," said Rajendra Pachauri, head of the U.N. panel of climate scientists.
He said costs of containing global warming would rise the longer the world waited.
The talks are seeking to find a successor to the U.N.'s existing Kyoto Protocol, which obliges rich nations except the United States to cut greenhouse gas emissions by an average of 5.2 percent below 1990 levels by 2008-2012.
Kyoto backers say they will only deepen their cuts, shifting from fossil fuels to clean energies like wind or solar power, until 2020 if the United States and big emerging economies led by China and India take on binding curbs.
Developing nations say they need to burn more energy, increasing greenhouse gas emissions, to fight poverty. U.S. President Barack Obama's hopes of legislating greenhouse gas cuts vanished after Republican gains in mid-term elections.
Success would help get the talks back on track after the acrimonious Copenhagen summit agreed to a non-binding deal to limit a rise in world temperatures to 2 degrees Celsius (3.6 degrees F) above pre-industrial times.
Failure would raise questions about the future of Kyoto, which underpins prices in carbon markets. Unless a new round is negotiated, Kyoto will end in 2012, leaving a patchwork of national measures to combat climate change.
"The stakes in Cancun are high. In the run-up to Copenhagen there was perhaps too much hype, and expectations were too high. Now we must avoid the opposite, that the bar is lowered too much," Danish Climate Minister Lykke Friis said.
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