UN negotiators staggered to an unsatisfactory agreement on Saturday around a bitterly disputed worldwide pact to stave off global warming.

While dozy delegates congratulated themselves on the outcome, which followed 36 hours of non-stop haggling at the end of a fortnight of talks, observers and threatened nations said that there wasn't much to be happy about.

Climate economist Nicholas Stern warned: "The actions that have been agreed are simply inadequate when compared with the scale and urgency of the risks that the world faces from rising levels of greenhouse gases and the dangers of irreversible impacts."

Rich and poor nations had been at loggerheads ever since the talks opened on November 11 over who should do what to restrict and reverse climate change.

Countries agreed on a consensus text outlining the road to a new global warming pact to be signed in Paris by 2015.

But the agreement relied on fudges such as replacing the word "commitments" to emissions cuts, with "contributions."

The negotiations faced collapse on Friday amid squabbling between developed and developing nations over their respective contributions to the process.

Emerging economies like China and India objected to any reference in the Warsaw text to "commitments" that would be equally binding to rich and poor states and failed to consider historical greenhouse gas emissions.

And hundreds of members of environmental organisations had walked out of the talks in protest at the lack of progress.

"As the intense discussions showed, there are serious differences between countries on the tough issues involved in getting a climate deal in Paris in 2015," said climate analyst Alden Meyer of the US-based Union of Concerned Scientists.

The final text did not mention any figures or set any targets.

"This conference should have been a finance conference," said Bangladeshi negotiator Qamrul Chowdhury. "But all we got were peanuts."

And Action Aid spokesman Harjeet Singh noted that "it is the barest minimum that was supposed to be achieved at Warsaw on loss and damage anyway.

"A few rich countries including the US held the talks hostage till the very end," he said.