The United States and China appeared close to agreement Wednesday on a key issue that has troubled climate change negotiations, boosting prospects that talks on global warming will score their first success in years.
Analysts said the tone over measuring emissions had softened between the two major protagonists in the 193-nation talks. Over the past year they repeatedly exchanged accusations of reneging on commitments and undermining the talks.
The much disputed issue involves how countries account for their actions to limit emissions of carbon dioxide and other heat-trapping gases and to what extent they will allow other countries to review their books. The process is known as measuring, reporting and verifying, or MRV in negotiating parlance.
Details remain to be worked out and MRV is only one of several elements that negotiators want to adopt as a package in Cancun.
"Maybe the differences are not that huge," said Su Wei, China's chief negotiator. "In general, both countries would like to promote the process" and emerge from Cancun with a deal.
The veteran diplomat said China had put in place a rigorous system for measuring and assessing its carbon emissions, and had no objection if other countries examined its reports. "We have no problem with MRV," he said.
Previously, China had said only some of its actions would be open to international scrutiny.
Earlier this week, U.S. negotiator Jonathan Pershing said the U.S. and China had "spent a lot of energy in the past month working on those issues where we disagree and trying to resolve them. My sense is we have made progress." He did not specify those issues.
The annual climate conference is the first since the Copenhagen summit last December, which broke up in acrimony after failing to reach a broad agreement binding industrial nations to deep emissions cuts and committing developing countries to move toward low-carbon growth.
Instead, the summit, which drew President Barack Obama, Chinese Premier Hu Jiantao and nearly 120 other world leaders, ended with a three-page statement of principles that fell short of the unanimous approval required by all parties.
This year, negotiators lowered their sights and were seeking to adopt a package of secondary issues that will keep the negotiations alive.
Kathrin Gutman, who follows the talks for the World Wildlife Fund, said an agreement on verification would be an important piece of a deal that could "unlock the larger discussion" on emissions reductions.
She said the two sides had refused to formally discuss the subject as recently as the last preparatory meeting a month ago, which was held in the Chinese city of Tianjin.
The shift apparently derived from compromise proposals by India and Singapore.
Barbara Finamore, the China expert for Natural Resources Defense Council, said the Chinese attitude at Cancun reflected "a sea change" in approach.
"China made a strategic decision to be as positive, open and forthcoming as they can," she said in an interview.