U.N. climate talks stalled after a rebellion by developing states most at risk from global warming, forcing host South Africa to push the conference into extra time on Saturday in an effort to prevent the negotiations collapsing.
Deliberations were due to resume around midday after haggling in the South African port city of Durban continued into the early hours.
South African Foreign Minister Maite Nkoana-Mashabane suspended the meeting late on Friday after a coalition of island nations, developing states and the European Union objected to a text they said lacked ambition.
Island states risk being swept away by the rising sea levels and extreme weather systems linked to global warming, which scientists say is the result of heat-trapping greenhouse gases released into the atmosphere by human activity.
Frustration has grown with hosts South Africa, which holds the annual presidency of the U.N. process, with many delegates complaining it has failed to do enough to broker a deal that better protects the poor countries it pledged to help.
Delegates accused South Africa of leaving too many contentious issues unresolved until the final hours and failed 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.
The European Union has been rallying 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.
The crux of the dispute is how binding the legal wording in the final document will be. The initial draft spoke of a legal framework, which critics said committed parties to nothing.
A new draft changed the language to legal instrument, which implies a more binding commitment, and says a working group should draw up a regime of emissions curbs by 2015.
It also turns up pressure on countries to act more quickly to come up with plans for reducing domestic emissions. Another issue is how deep emission cuts would be under a second phase of the Kyoto Protocol, the globe's only legally binding emissions treaty.
The changes should appeal to poor states, small island nations and the European Union, but may be hard to swallow for major emitters, including the United States and India, to swallow, said Alden Meyer, director of strategy and policy at the Union of Concerned Scientists.
One of the crunch issues that has been left out is the date by which the new agreement will enter into force, which could still be as late as 2020 and making it no better than the previous text on this issue, said Tim Gore, climate change policy advisor for Oxfam.
The delegates are also expected to debate text on a raft of other measures, including one to protect forests and another to bring to life the Green Climate Fund, designed to help poor nations tackle global warming.
The EU strategy has been to forge a coalition of the willing to try to pressure the world's top carbon emitters -- China, the United States and India -- to sign up to binding cuts. None of the big three is bound by the Kyoto Protocol.
EU Climate Commissioner Connie Hedegaard said a small number of states had yet to sign up to the EU plan and there was little time remaining for a deal in Durban.
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.
Many envoys believe two weeks of highly complex climate talks, bringing together nearly 200 nations, will at best produce a weak political agreement, with states promising to start debate on a new regime of binding cuts in greenhouse gases.
At worst, the talks could collapse, putting off agreement on the core issues until May next year. Failure in Durban would be a repeat of the 2009 climate summit in Copenhagen, which fell short of delivering a meaningful global deal to follow on after a first set of Kyoto carbon cuts.
U.N. negotiators regrouped in 2010 in Cancun, where a more modest programme of action and a set of voluntary pledges to curb carbon emissions were drawn up.
Scientists say those promises are not yet enough to limit global warming to the two degrees Celsius judged necessary to stave off the most devastating effects of climate change.
U.N. reports released in the last month show time is running out. 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.
The protracted talks have angered delegates from small islands and African states, who joined a protest by green groups on Friday as they tried to enter the main negotiating room.
You need to save us, the islands can't sink. We have a right to live, you can't decide our destiny. We will have to be saved, Maldives climate negotiator Mohamed Aslam said.
(Additional reporting by Barbara Lewis, Agnieszka Flak, Andrew Allan and Stian Reklev)