Negotiations aimed at clearing the way to next month's showdown on climate change in Copenhagen ran into problems on Tuesday as African countries demanded rich nations show their hand on curbing carbon emissions, delegates said.
Talks were suspended in one of the twin tracks of negotiations under the 192-nation UN Framework Convention on Climate Change (UNFCCC) as intermediaries grappled for a solution behind the scenes, they said.
African countries pointed the finger at advanced economies, accusing them of backsliding on showing how deep they would rein in their greenhouse-gas pollution.
They demanded emissions curbs of 40 percent by 2020, compared to 1990 levels, as a sign of good faith in the complex negotiations to craft a post-2012 climate treaty.
"Annex 1 countries must take the lead and put the numbers on the table," said Kenyan delegate Grace Akumu.
The protest affected negotiations in several groups meeting under the banner of the Kyoto Protocol, the cornerstone treaty of the UNFCCC.
The other branch of the negotiations -- the so-called "long-term cooperative action" -- includes Kyoto countries, plus the United States which has refused to ratify the Protocol.
Delegates at senior official level have until Friday in Barcelona to whittle down a bulging draft text into something manageable for the December 7-18 talks in Copenhagen.
The goal is a treaty that will take effect after 2012 when current pledges of the Kyoto Protocol expire, setting medium- and long-term goals for taming global warming.
It would identify emissions curbs and craft mechanisms that would potentially pump billions of dollars into poor countries to help them switch to a low-carbon economy and shore up their defences against climate change.
Scientists warn that on present trends, Earth's climate system could be catastrophically damaged by higher temperatures, leading to more frequent and brutal droughts, higher sea levels, and floods and storms.
A goal favoured by the European Union (EU), the Group of Eight (G8) and the world's major economies forum is to limit concentrations of greenhouse gases to less than 450 parts per million (ppm).
This is equivalent to a rise of around two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial times.
To achieve such a goal, rich nations must aim for carbon pollution cuts between 25 and 40 percent by 2020 compared with 1990 levels, the UN's Intergovernmental Panel on Climate Change (IPCC) said in 2007.
So far, only two big economies -- the EU and Japan -- have got anywhere near the target.
The EU has unilaterally decided to cut its emissions by 20 percent by 2020, and offered to go to 30 percent if another major player follows suit. Japan has offered a cut of 25 percent.