"It's an important voice on the developing country side. But I think India also has great potential to speak from a posture of credibility, frankly, on kind of both sides of the aisle, if you will," said Todd Stern, the Special US Envoy for Climate Change.

Stern was talking to foreign correspondents ahead of the United Nations Climate Change meeting at Cancun in Mexico.

"India had a very important role last year in Copenhagen, and I think India will have a very important role this year, particularly if we have a chance of getting anywhere.

"I think India has shown both a commitment to principles but also a willingness to think in a new way and to be pragmatic. I think that's been quite important," Stern said in response to a question.

The challenge, he said, in Cancun is to find a way to build on the progress made last year in the Copenhagen Accord through the direct intervention of many of the world's leaders.

Representatives from 194 nations will meet in the Mexican resort city of Cancun from November 29 to December 10 to clinch an agreement to curb greenhouse gases after 2012.

"Even though it fell short of what many had hoped for, the accord took an important step forward in addressing climate change. Progress was made on all the key elements of the negotiations, and much of it in direct, face-to-face discussions among our leaders," he said.

"In essence, the accord included, on the one hand, landmark provisions for financing in order to support mitigation, adaptation, technology, and forest preservation - the so-called red issue - all of these things redounding to the benefit of developing countries that on the one hand, and on the other hand, a crucial agreement among both developed and developing countries to implement a set of mitigation either targets or actions, and to do so in an internationally transparent manner," he said.

"What we are seeking now in Cancun is a balanced package of decisions on these points, decisions being a term of art in the framework convention.

"It is now widely understood that a legal treaty this year is not in the cards. There is broad convergence on the notion that a package of decisions is desirable and the devil will most certainly be in the details. To preserve the balance of the package in Cancun, we need to make comparable progress on all the core issues included in the accord," said the US official.

Stern said there is a vision of progress within the reach that would start with first a set of solid decisions this year that includes an adequate level of detail on each of the core issues - mitigation commitments, a green fund, transparency, technology, and so forth.

"Second, followed by a concentrated follow-on process for 2011, such as special working committees in which the remaining detail on all of these issues would be elaborated.

And then this process would conclude with the third step, which would be fully operational decisions," he said.

"None of this would preclude or prejudge an eventual legal treaty when the time is right, but our view is that we should be making concrete progress now.

"In the often repeated view of the United States, a treaty requiring legally binding mitigation commitments from the US, the EU, Australia, Japan, other developed countries; would have to also require them of China, India, and other emerging economies, and we just don't see this happening soon," Stern said.

"So rather than insisting on a legal treaty before anything happens, we should move down the pragmatic path of concrete operational decisions. And again, if we do this right, we can, in relatively short order, start standing up a green fund, create a new technology mechanism, start implementing significant mitigation commitments, put in place a system of transparency and accountability, and make real progress on adaptation and forest protection," he said.