The action forced several technical meetings to be cancelled, while the 50 or so African countries said they would only discuss pledges submitted by wealthy countries.
Delegates to the UN climate talks in Barcelona warned that, unless the African protest was settled, it could set back the timetable for concluding a new climate change pact at a major UN conference next month in Copenhagen.
The African countries say they are the most vulnerable to climate change yet the least responsible for the accumulation of carbon in the atmosphere that is causing global warming.
A landmark 2007 UN report based on the work of about 2,000 scientists predicted Africa would suffer the most from drought, agricultural damage, rising sea levels threatening coastal areas and the spread of tropical pests and diseases.
Scientists say industrial countries should reduce emissions by 25 to 40 per cent from 1990 levels by 2020, but targets announced so far amount to far less than the minimum.
Talks were under way to try to resume the closed-door meetings on technical issues related to emissions reductions, including identifying new greenhouse gases to be regulated and setting rules by which rich countries might offset emissions with green technology investments in poor countries.
In London, UN Secretary-General Ban Ki-moon admitted that the climate change treaty may not be resolved this year, as nations may be unable to commit to firm emissions limits at Copenhagen.
"Copenhagen will be a very important milestone. At the same time, realistically speaking, we may not be able to agree on all the words," Ban said after holding talks with British Prime Minister Gordon Brown.
Ban said he would push leaders to strike a pact in Copenhagen, but that it was more likely to be an agreement on principles rather than specific targets for cuts.
"We need at this time the political will if there is a political will, there is a way we can come to a binding agreement in Copenhagen," Ban said.
The Copenhagen deal would succeed the 1997 Kyoto Protocol, which called on 37 industrial countries to reduce emissions of heat-raising gases by an average 5 per cent below 1990 levels by 2012. It made no demands on major developing countries like India and China. The United States was the only major greenhouse gas emitter to reject the Kyoto accord.
The U.S., which says it wants to be part of the Copenhagen deal, has been criticized for delaying any announcement at the climate talks of its emissions target. The U.S. delegation says it is waiting for Congress to finish work on climate and energy legislation. Those bills suggest the U.S. would cut emissions only about 4 per cent below 1990 levels over the next decade.
The U.S. came under renewed pressure to declare its intentions at the UN talks before the decisive Copenhagen meeting from December 7-18.
Denmark's minister for climate and energy, Connie Hedegaard, noted that President Barack Obama would be in nearby Norway accepting the Nobel Peace Prize while the Copenhagen conference is under way. She said it was "hard to imagine" that Obama, who was cited by the Nobel committee for his climate-friendly policies, would send his delegation to Copenhagen empty-handed.