South Africa struggled on Saturday to find a compromise deal that could save U.N. climate talks from collapse.
Ministerial negotiations in the South African port city of Durban were put off until Saturday afternoon but with many delegates due to head home there was a strong chance real decisions would be put off until next year.
That would be a major setback for host South Africa and raise the prospect that the Kyoto Protocol, the only global pact that enforces carbon cuts, could expire at the end of next year with no successor treaty in place.
They're working. They're working hard. You have to give them time to work, U.N. climate chief Christiana Figueres.
South African Foreign Minister Maite Nkoana-Mashabane late on Friday drafted fresh proposals after an initial draft was angrily rejected by the poor states most at risk from the devastating effects of global warming.
However, those changes have failed to secure a consensus. Developing states and the European Union said the latest document contained no reference to how the fight against climate change would be paid for and set no date by when cuts to emissions must be decided.
The text also deferred decisions on cutting emissions from international aviation and shipping to next year.
The political coalition is there to get an ambitious result, but we are almost literally working against the clock, said Britain's climate secretary Chris Huhne.
We can go on and we will go on as long as it takes, but there is a risk that a number of other delegations will, for one reason or another, will have to peel away, he said.
We're working very hard within those time constraints to get a successful outcome ... We are in the hands of the (South African) presidency as to the next steps.
The European Union has tried to rally support for its plan to set a date of 2015 at the latest for a new climate deal that would impose binding cuts on the world's biggest emitters of heat-trapping gases. Any deal could then come into force up to five years later.
But Washington says it will only pledge binding cuts if all major polluters make comparable commitments. China and India say it would be unfair to demand they make the same level of cuts as the developed world, which caused most of the pollution responsible for global warming.
Ministers are meeting to decide if they can agree on the big picture document and the Kyoto protocol text. If they can't agree it is possible there won't be an agreement, said Samantha Smith, leader of global climate and energy initiative at WWF International.
One diplomatic source told Reuters: The worst scenario is there will be no agreement on the core issues and it will go to next year.
Delegates in Durban have also been discussing a raft of other measures, whose fate would be unclear if the talks ended inconclusively.
They include measures to protect forests and another to bring to life the Green Climate Fund, designed to help poor nations tackle global warming.
U.N. reports released in the last month show time is running out to restrict global warming to safe limits, generally accepted as within a 2 degree Celsius rise in average global temperatures. A warming planet has already intensified droughts and floods, increased crop failures and sea levels could rise to levels that would submerge several small island nations.
Many of their delegates are frustrated that South Africa has failed to do enough to broker a deal that better protects the poor countries it pledged to help and failing to show the leadership needed to push through settlements.
They have let agreements slip through their fingers. If we do reach any outcome that advances the process, it will not be because of South Africa's leadership. It will be despite South Africa, said one envoy.
(Additional reporting by Barbara Lewis, Agnieszka Flak, Andrew Allan and Michael Szabo; editing by Jon Boyle)