China is leading objections to a major report on climate economics being discussed at a Bangkok conference.
Delegates from 120 countries are attending the IPCC meeting
A draft copy of the report concludes that the world's climate can be stabilised at a reasonable cost, as long as nations act now.
But correspondents say the Chinese see the document as a potential threat to their economic growth.
The report is being discussed at a meeting of the Intergovernmental Panel on Climate Change (IPCC).
Two reports issued earlier this year by the same UN panel warned that the earth was already warming considerably, and that mankind was almost certainly to blame.
They predicted severe consequences including droughts, floods, storms, heat waves and rising seas.
This latest report is designed to look at how the world can mitigate rising levels of greenhouse gases.
Environmentalists argue that while it will need investment to put these policies into practice, the eventual consequences of doing nothing far outweigh the cost of tackling global climate change now.
Exactly what action to take, and how much it will cost, is likely to be the main topic of debate during the closed-door meeting, which began on Monday and is due to end with the announcement of the final report on Friday.
The draft, seen by the BBC, suggests various solutions to mitigate climate change, such as capturing and burying emissions from coal-fired power plants, shifting to renewable forms of energy and more use of nuclear power.
If the delegates stick with the tone of the draft, the report is likely to remove any justification for rich nations like the USA to avoid emissions cuts on the grounds of cost.
But correspondents say early indications from inside the conference suggest that the US is actually not objecting to much - it is China that is being really obstructive.
China's emissions are just one-sixth of America's per capita, but the population is so huge that this year the country is due to become the world's biggest polluter.
The Chinese fear that if this UN document is agreed, it will increase pressure on them to cut emissions so heavily that it could derail their drive to create jobs and lift millions of people out of poverty.
The findings of the report will be used by governments and international organisations to map out their own plans for climate change mitigation.
"The IPCC plays an incredibly important role in the political negotiations so people can point and say 'Look, this is what is going to happen in 50 years, these are the options available for us to take actions'," UN Environment Programme spokesman Michael Williams said on Monday.
The report's conclusions will play a key role in negotiations on the Kyoto Protocol, which will take place in December on the Indonesian island of Bali.
It will also influence world leaders when they meet face-to-face for climate change talks at the summit of the group of eight most industrialised nations (G8) in June.