"The train to Copenhagen has left the station," said Yvo de Boer, Executive Secretary of the United Nations Framework Convention on Climate Change.

"Not only do we have the certainty that critical issues will be addressed next year, we now have bit-sized chunks which will allow us to negotiate in an effective manner," he told a news conference at the conclusion of the week-long Bangkok talks.

The next meeting, to be held in Germany in June, will address the issue of funding and technology to mitigate climate change, a key demand of developing nations who argue that rich countries should foot much of the bill.

A suggestion pushed by Japan in Bangkok to take a sectoral, rather than purely national, approach to emissions cuts was deferred to the third round of talks.

United Nations climate experts want the new treaty that emerges from Copenhagen to go beyond Kyoto by getting all countries to agree to curbs on emissions of the greenhouse gases that are fuelling global warming.

Under Kyoto, only 37 rich nations are bound to cut emissions by an average of five percent from 1990 levels by 2012.

A UN climate panel agreed last year that the world needs to halve its greenhouse gas emissions by 2050 in order to stave off potentially catastrophic changes to the weather system, that will bring more storms, droughts and higher sea levels.

Negotiators will also have to work out how to deal with the United States -- the only rich nation not to have signed up to Kyoto -- given that President George W. Bush will be leaving the White House after November's election.

Bush pulled the United States out of Kyoto in 2001, saying the pact would hurt the economy and was unfair since it excluded big developing nations from committing to emissions cuts.

The White House has since moderated its stance by saying it would accept emissions targets if all other big emitters do as well based on their individual circumstances.