Modest progress at U.N. climate talks Saturday was overshadowed by a continuing deadlock between China and the United States, clouding prospects for a major climate conference in Mexico in less than two months' time.
Marred by an atmosphere of mistrust, negotiations have made limited headway as the world's two largest emitters of greenhouse gases blamed each other for holding up talks.
Chief U.S. negotiator Jonathan Pershing said he was disappointed by the resistance of China and other developing nations to a major issue: allowing the monitoring and verification of their efforts to curb the greenhouse gas emissions that are blamed for global warming.
"We have made very little progress on the key issue that confronts us," he said. "These elements are a part of the deal. The lack of progress on these gives us concern about the prospects for Cancun."
Meanwhile his Chinese counterpart, Su Wei, hit back, charging developed countries with failing to commit to substantial reductions in carbon emissions while making unfair demands of developing nations. He accused the U.S. of using the transparency issue to avoid its own responsibilities to cut emissions and provide financing and technology to poor countries.
"After five years of negotiation, we have seen slow or no progress. The developed countries are trying every means possible to avoid discussion of the essential issue _ that is emission reductions," he said.
The public rift over long-standing divisions between rich and poor nations threatens to jeopardize the possibility of progress at the Cancun meeting.
Delegates from more than 150 nations have been negotiating in China's northeastern city of Tianjin for the past week, working to lay the groundwork for the meeting in Mexico that starts Nov. 29.
The U.N. talks aim to secure a binding deal to curb greenhouse gases that cause global warming, but countries disagree on how to split the burden of emission cuts and how to verify them. The talks are intended to find a replacement for the Kyoto Protocol, which legally mandated modest emissions reductions and expires in 2012.
Since a binding global deal is largely out of reach for this year's meeting, negotiators have been focusing on less contentious initiatives that can lay the foundation for a legal framework that could be approved later, possibly in South Africa in 2011.
On their final day of talks, negotiators said modest progress had been made on establishing a climate fund to help poor nations, drawing up guidelines on sharing technology and deforestation issues, but expressed frustration at the overall gridlock.
"We have over the last week seen some progress but progress was slow and uneven," said EU negotiator Peter Wittoeck. "We think that a big effort will still be needed to crystallize options ... in Cancun.
Environmental groups were divided in their assessment of the week's talks, with many openly criticizing the bickering and posturing that characterized negotiations.
"At times, it has been like watching children in a kindergarten," said Wendel Trio, international climate policy director with Greenpeace.
However, others were less pessimistic, arguing that the detailed work of putting together draft proposals for Cancun has moved forward.
"We have heard of a lot of division and argument, but much of that has been performance and part of the negotiations here. Behind the scenes, they have been getting down to work this week," said Julie-Ann Richards of Climate Action Network.
Expectations had not been high coming into these negotiations, but U.N. climate chief Christiana Figueres said that despite disagreements, progress had been made in Tianjin.
"This week has got us closer to a structured set of decisions that can be agreed to in Cancun. Governments addressed what is doable in Cancun, and what may have to be left to later," she said.
Last year's U.N. climate summit in Copenhagen disappointed many environmentalists and political leaders when it failed to produce a legally binding treaty on curbing the greenhouse gases.
Scientists have warned that global warming could lead to widespread drought, floods, higher sea levels and worsening storms. Even a 3.6-degree-Fahrenheit (2-degree-Celsius) temperature rise could subject up to 2 billion people to water shortages by 2050, a U.N. panel has said.
Associated Press Writer Joe McDonald contributed to this report.