More than 150 nations meet in Ghana today in an effort to speed up sluggish talks on a new climate treaty and plug big gaps in a vision of leading industrial nations to halve world greenhouse gas emissions by 2050.
The August 21-27 meeting of 1,000 delegates will also consider new ways to combat global warming such as slowing tropical deforestation - UN studies say burning of trees accounts for about 20 per cent of greenhouse gases from human activities.
"While progress has been made, there is no doubt that we need to move forward quickly," Yvo de Boer, head of the UN Climate Change Secretariat, said in a statement.
The Accra meeting will be the third since governments agreed last year to negotiate a new climate treaty by the end of 2009 to avert threats such as heatwaves, rising sea levels, disruption of monsoons, desertification and flooding.
Slowing economic growth in many nations, the collapse of world trade talks in July and uncertainties about US policy after President George W. Bush leaves office in January means that many countries are wary of showing their hands.
"The political process has suffered major delays and is far from where it should be," the WWF conservation group said.
The talks will be a first chance to ease tensions between rich and poor nations after leaders of the Group of Eight industrialised nations agreed at a summit in Japan last month on a vision of halving world greenhouse gas emissions by 2050.
Major developing nations including China and India refused to sign up to any 2050 goal in talks with G8 leaders, saying rich countries had burnt most fossil fuels since the Industrial Revolution and should first set tougher cuts for themselves.
"I don't see that (2050 goal) as very helpful...since it's so far away," said Harald Dovland, a Norwegian official who will preside in Accra over talks by nations that support the current UN Kyoto Protocol for curbing emissions until 2012.
"A 2050 signal is okay but doesn't give us a real basis for agreeing on needed short-term targets," he said. Most of today's politicians will be dead or have retired by 2050.
Many want a UN treaty to set 2020 goals to guide investors - for instance trying to decide whether to build a coal-fired power plant or put cash into solar or wind power.
One strategy to ease disputes between rich and poor is to offer developing nations credits for curbing deforestation. Trees store carbon as they grow and release it when burnt.
New Zealand said in a note to the Accra negotiators that financial incentives to make a significant dent in deforestation would have to be in the range of $10 to $40 billion a year.
But some environmentalists fear that projects for slowing deforestation might backfire if they let rich nations buy up tracts of forest to gain carbon credit that can count as cuts in emissions against domestic targets.
"Great land grab threat at UN climate talks in Ghana," Friends of the Earth International said. It said indigenous peoples in forests might be forced out if investors buy them up.
Environmentalists say talks are lagging compared to 1996-97 negotiations on the Kyoto Protocol, binding 37 developed nations to cut emissions by five per cent below 1990 levels by 2008-12.
The US is the only developed nation outside Kyoto. Bush said it would cost too much and wrongly excluded 2012 targets for developing countries.
Both main Presidential candidates, Democrat Barack Obama and Republican John McCain, say they would adopt tougher policies than Bush.