| CANCUN, Mexico
CANCUN, Mexico The world's governments struggled on Wednesday to break a deadlock between rich and poor nations on steps to fight global warming and avert a new, damaging setback after they failed to agree a U.N. treaty last year in Copenhagen.
They face yawning gaps over the future of the Kyoto Protocol for curbing emissions by rich nations until 2012. Japan, Canada and Russia say they will not extend the pact unless poorer nations also commit to emissions cuts, while emerging economies led by China insist the developed world must first deliver results.
Mexican Foreign Minister Patricia Espinosa, looking tired 10 days into the talks in the Mexican beach resort of Cancun, cautioned that much work was left to agree steps meant to slow ever more heat waves, droughts, floods and rising sea levels.
"I believe that an ambitious, broad and balanced package is within reach," she told delegates at the negotiations that are due to end on Friday. "That does not mean that we already have it in our grasp."
Negotiators aim to set up a new fund to help developing countries combat climate change, work out ways to protect tropical forests, help poor nations adapt to climate change and agree a new mechanism to share clean technologies.
Failure to achieve even those modest steps would be a further blow to the U.N. process after U.S. President Barack Obama and other world leaders could only manage a vague, non-binding deal in Copenhagen in 2009, when many had pinned hopes on a treaty.
"Failure ... is not an option, or we risk accelerating the erosion of confidence and the legitimacy of the U.N. talks as the forum to solve climate change," said Samoa's prime minister, Tuilaepa Lupesoliai Neioti Sailele Malielegaoi.
Alden Meyer of the Union of Concerned Scientists, a U.S.-based group campaigning for a healthy environment, said the talks could not withstand two successive setbacks.
"Here it's two strikes and you're out," Meyer said, adapting a baseball metaphor where batters usually get three tries to hit the ball.
Confidence in the U.N. talks has already been hit by Copenhagen, which agreed only a non-binding deal to limit a rise in average world temperatures to below 2 degrees Celsius (3.6 F) above pre-industrial times.
Without success in Cancun, faith in the seemingly endless U.N. talks could wither away.
The need for any deal be agreed unanimously -- from the poorest countries in Africa to the United States -- complicates the U.N. talks, especially in an era of shifting global power.
Norwegian Prime Minister Jens Stoltenberg said some countries were backtracking even on agreements made in Copenhagen, such as a 140-nation deal that the rich would provide $100 billion in aid a year from 2020.
Proposed texts circulating in Cancun give options both of $100 billion, and a far higher 1.5 percent of rich nations' gross domestic product in aid. He warned poor nations that asking for more aid might mean the rich cut -- rather than raise -- the $100 billion offer.
"The outcome of Cancun is uncertain," he said.
The Cancun meeting has become largely hung up over the future of the Kyoto Protocol, which obliges almost 40 rich nations to cut emissions by an average of 5.2 percent below 1990 levels during the five-year period 2008-12.
China, India and other developing nations say that Kyoto members must extend the pact beyond 2012 before poorer countries sign up for curbs. Kyoto members, with Japan the most hardline, say they are committed to it until 2012 but that all nations must then agree a new treaty.
(Writing by Alister Doyle;Editing by Kieran Murray)