The two-week conference in Cancun aims to agree on funds and approaches to preserve rain forests and prepare for a hotter world. It will also seek to formalize existing targets to curb greenhouse gas emissions.

Fanfare is far below levels of last year's Copenhagen summit which aimed to agree a new climate deal but ended instead with a non-binding agreement rejected by a clutch of developing countries. The long-running U.N. talks have pitted against each other the world's top two emitters, the US and China, with U.S. demands for greater Chinese emissions curbs.

On the eve of the talks, Mexican President Felipe Calderon pointed to the economic opportunities from fighting climate change, aiming to end the distrust of the previous summit.

"This dilemma between protecting the environment and fighting poverty, between combating climate change and economic growth is a false dilemma," he said pointing to renewable energy as he inaugurated a wind turbine to power the conference hotel.

In a keynote speech opening the conference, Calderon said: "The atmosphere is indifferent to the sovereignty of states," and “it would be a tragedy if our inability to see beyond our personal interests, our group or national interests makes us fail."

Reuters-AP