* Mexico says results a must at climate meeting
* "Breakthrough" still possible at December negotiations
MEXICO CITY, Aug 16 (Reuters) - Mexico hopes to "rescue" global climate change talks by hosting a successful summit later this year that ends in concrete actions to control greenhouse gases, its chief negotiator said on Monday.
Expectations for a decisive climate change agreement this year have been lowered as negotiators and United Nations officials cautioned that major stumbling blocks persist with just a few months before the December meeting in Cancun, Mexico.
"We will not be able to negotiate a new treaty in Cancun, that much is clear," Mexico's chief delegate Fernando Tudela told Reuters in an interview. "But that does not mean that there can't be a spectacular breakthrough."
One goal is to dispel the mistrust that has clouded climate diplomacy since the failure of last year's Copenhagen summit.
"We need to be rescued from the regime standoff left over from Copenhagen," said Tudela, a senior official of Mexico's Ministry for the environment and natural resources.
"We have to achieve confidence, unity, and effectiveness... We need to get back trust in building an inclusive system."
Most countries at Copenhagen signed up to an accord that called on governments to limit the rise in global temperatures to less than 2 degrees Celsius (3.6 Fahrenheit), but without spelling out how to achieve this goal.
Rich nations and rapidly industrializing countries like China and India remain far apart on who should bear the brunt in cutting greenhouse gas emissions.
Many developing nations want the rich world to make deep emissions cuts before they will consider curbs of their own.
Negotiators have been discouraged that climate talks sponsored by the United Nations in Bonn earlier this month ended with countries widening, not narrowing, the number of disputed issues.
This month, U.N. Secretary-General Ban Ki-moon acknowledged the Cancun meeting might not produce the definitive agreement the world body is seeking.
Cancun must make progress on some concrete issues like financing and preparing for a warmer future, Tudela said.
"We need to achieve a set of meaningful decisions," he said. "We have a window of opportunity that is closing... What we want to do is rescue these negotiations." (Reporting by Caroline Stauffer and Patrick Rucker; editing by Chris Wilson)
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