UN climate talks entered a second day of extra time amid deadlock and bitterness as the United States warned failure to compromise could doom the 22-year-old global forum.
Supposed to have ended a 12-day run on Friday, the negotiations were mired more than 24 hours later in a row between rich and poor countries over sharing out responsibility for tackling climate change.
Chairs of a working group tasked with formulating a text presented negotiators with a laboriously-crafted compromise, only to see it shot to pieces.
Many rich nations accepted it as a workable blueprint.
But developing countries kicked it out, saying the document failed to balance action on tackling Earth-warming carbon emissions with help for vulnerable economies.
US envoy Todd Stern said the stalemate put at risk a climate pact due to be signed in Paris in 2015, as well as the credibility of the UN Framework Convention on Climate Change (UNFCCC) -- an offshoot of the 1992 Rio Earth Summit.
"All we have achieved so far will be at risk, and all that we hope to achieve will be at risk as well," Stern warned delegates.
"The success of this COP here in Lima is at stake," he said, using the jargon for the UNFCCC's annual Conference of Parties.
"The success of next year's COP in Paris is at stake, and I think the future of the UNFCCC as the body to address climate change effectively at the international level is also at stake."
Facing division, exhaustion and an increasingly fractious mood, the working group handed the baton of seeking a compromise to conference president Manuel Pulgar-Vidal, Peru's environment minister.
"Currently they will be deciding whether to put back in some of the elements needed in the Paris agreement... or to strip out every contentious paragraph and start all over again next year," suggested Mohamed Adow of campaign group Christian Aid.
"Wasting an entire year's worth of work, though, (will) not only be bad for the planet and the people already suffering climate impacts, but will also be embarrassing for everyone involved from the co-chairs to the nations themselves."
Negotiators in Lima must agree on a formula for guiding a process next year of declaring national carbon-curbing pledges.
These will form the backbone of the 2015 Paris accord to limit global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial levels.
To take effect by 2020, the world pact would for the first time bring all 196 UNFCCC members into a single arena for cutting greenhouse gases.
After a buoyant start, the Lima talks ran into familiar backbiting about which countries should do more in the war on climate change.
Developing nations insist the West must bear a bigger burden for carbon cuts, having started decades earlier to pollute their way to prosperity.
But rich countries point the finger at developing giants like China and India, furiously burning coal to power their rapid growth.
- Anger over adaptation help -
Developing countries also want rich nations' carbon pledges to include commitments to financial help and adaptation aid for shoring up their climate defences.
"Let us not forget millions of poor, because every climate action has a cost," said Indian Environment Minister Prakash Javadekar.
Malaysia complained that appeals for wording on adaptation help had fallen on deaf ears.
"What else do you want us to do? To go on bended knee?" its delegate asked.
Campaigners in Lima lashed the proposed compromise, saying it had simply sought the lowest common denominator and would do little to provide guarantees of serious measures for rolling back fossil fuel emissions or helping those in need.
Apart from the pledge format, negotiators must also agree in Lima on a workable negotiating outline for the Paris pact, with less than a year of haggling time left.
Scientists say the two-degree target is roughly half the warming that can be expected by 2100 on current emissions trends, placing the world on track for more frequent and severe droughts, floods, storms and fast-rising sea levels.
Emissions must be slashed by 40-70 percent by 2050 from 2010 levels and to near zero or below by 2100 for a good chance of reaching two-degree warming, the UN's Intergovernmental Panel on Climate Change said in a report  this year.