The accord is being considered a major achievement with respect to the Kyoto agreement, in a crusade against climate change.
However, last minute negotiations over a Japanese proposal did not augur well with the poorer nations.
Leaders from the developing bloc opposed Japan's proposal of "sectoral approach", in which each industry was to be judged separately on eco-friendliness.
Developing nations fear the sectoral approach makes the aims of Kyoto protocol easier to be met by rich countries.
Daniel Mittler, climate and energy adviser for Greenpeace International, said: "The Japanese proposal is the main stumbling block."
"This meeting should be about saving the planet, not the G8 summit."
However, Kyoji Komachi, Japan's chief negotiator, said Tokyo was seeking only a discussion of the sectoral idea and was ready to commit major resources to help developing nations fight global warming.
Japan, which is far behind in meeting its Kyoto obligations as its economy recovers from a recession, hopes to shape the next global climate treaty when it hosts the G-8 summit in July this year.
Alden Meyer, strategy director for the Union of Concerned Scientists, a US pressure group, said: "They're setting the table for a meal and they haven't really digged in."
"That means there's no food fight, but that will come down the road when it gets serious," said Meyer.
Almost all delegates agreed that the toughest issue about slashing gas emissions after 2012, when the Kyoto protocol officially ends, would have to wait until the United States got a new president in January 2009.
George Bush, the US president, had specifically backed out of the Kyoto protocol, arguing that it was too costly and unfair by making no demands of emerging economies such as China.
"I think people are optimistic that the next administration in the US is going to engage in a different way than Bush has," Meyer said.
The Kyoto protocol required rich countries to slash emissions blamed for global warming, by an average of five per cent by 2012, from the base levels of 1990.
However, it exempted aviation and shipping, two rapidly growing sources of global warming.
The European Union has proposed that rich nations slash gas emissions by 25 to 40 percent by 2020 from the 1990 levels.
The United States has not backed a clear figure and has insisted that developing countries make clear commitments in the next phase.
Rich and poor countries are divided on how to tackle the issue, despite growing fears that rising temperatures could put millions of people at risk by the end of the century.
The Bangkok meeting is the first since a major conference in Bali, Indonesia in 2007, which discussed what should be done after the commitment of rich countries to the Kyoto protocol ends in 2012.