Representatives from 192 countries are gathering for the Copenhagen climate summit, which some scientists have described as the most important conference the world has ever seen.
About 100 leaders are expected to attend over the next two weeks, where developing countries will discuss whether to demand tougher emissions cuts than have been put forward so far.
UN climate negotiator Yvo de Boer has said the talks were in excellent shape and has told the BBC that many countries were now trying to curb greenhouse gas emissions.
Mr de Boer said offers of finance for clean technology for poor countries were also coming through and talks were progressing on a long-term vision of massive carbon cuts by 2050.
South Africa has become the latest country to make an offer on cutting emissions, which will be its first quantifiable target.
Yesterday South Africa offered to cut by one-third the growth of its carbon emissions over the next decade – subject to getting more funding and technological help from wealthier countries.
China, the world's largest emitter of greenhouse gases, says it is threatened by global warming and the shrinking glaciers, expanding deserts, prolonged droughts and more intense storms predicted to come with a warming world.
Any agreement made at Copenhagen is intended to replace the 1997 Kyoto Protocol on climate change. Targets set at Kyoto run out in 2012.