BARCELONA - With U.S. legislation on reducing carbon emissions caught up in political wrangling and many other nations waiting to see what the United States does before making their own firm commitments, prospects are fading that a legally binding new pact to limit climate change will be signed at Copenhagen in December.

That has caused immense frustration at climate talks in Barcelona this week, the last negotiating sessions before Copenhagen.

African nations – working together as a separate pressure group for the first time in climate negotiations – boycotted one day of the talks, forcing the cancellation of some meetings.

On Friday, as the negotiations closed with only limited progress, Ibrahim Mirhani Ibrahim, head of Sudan's delegation, expressed disappointment that developed nations were promising only 11 to 15 percent cuts in emissions by 2020, far short of the 40 percent cuts developing countries believe are needed to avoid the worst effects of climate change.

The limited ambition of the promises "takes us on a very dangerous path," he warned in a press conference. "Between now and Copenhagen we need a real change of heart and mind by developed countries and that real change will only be demonstrated by figures."

Figures on firm emissions cuts by 2020 and 2050, however, are only part of what is still needed for success at Copenhagen, said Yvo de Boer, the UN's climate chief.

For an effective deal to be signed, developing countries need to present plans to limit the growth in their emissions, he said. Clear long-term funding for climate adaptation in poorer countries needs to be agreed, with $10 billion in start-up funds put on the table at Copenhagen. And negotiators need to agree on a structure to manage and hand out that money, including an equitable and lasting formula on how it should be divided among nations in need, to avoid future wrangling.

"After Copenhagen, talking action must turn to taking action," he said, even if work to agree the fine points of the deal stretches into next year.

The alternative to reaching a effective deal is bleak, researchers and campaigners at the Barcelona meeting said, and not just for the world's poorest and most vulnerable nations who are most at risk from climate change.

"Rich countries must recognize that tens of thousands of forced climate migrants, increased food shortages and spiraling climate debt is not just a reality faced by poor nations, but will ultimately affect us all," said Antonio Hill, a climate adviser for Oxfam, an organization aimed at fighting poverty and injustice.

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