UN chief Antonio Guterres urged rich and developing nations to stop the "finger pointing" at crunch climate talks on Thursday and reach a deal on covering the losses suffered by vulnerable nations battered by weather disasters.
With the two-week COP27 conference officially due to wrap up on Friday, negotiators in Egypt said the talks would likely go on overnight as they scramble to find a compromise over the contentious "loss and damage" issue.
Guterres said there was "clearly a breakdown in trust" between developed and emerging economies, adding that the most effective way to build confidence would be to find an "ambitious and credible agreement" on loss and damage and financial support for vulnerable countries.
"This is no time for finger pointing. The blame game is a recipe for mutually assured destruction," he said.
"The time for talking on loss and damage finance is over -- we need action," he said, after flying back to Egypt from Bali where he had attended a G20 leaders meeting.
The intervention from the UN chief comes as the climate talks teeter on the edge of failure as poorer countries least responsible for global emissions lock horns with rich polluters over the creation of a "loss and damage" fund.
Ralph Regenvanu, minister of climate change for the Pacific island of Vanuatu, said walking out of the talks "was discussed as an option" if developing nations come away empty handed.
"We are out of time and we are out of money and we are out of patience," he said at a news conference.
"We must establish at this COP27 a loss and damage finance facility."
A 130-nation group known as G77+China issued a proposal to create the fund at the COP27 and agree on the nitty-gritty details at the next UN talks in Dubai in 2023.
After dragging their feet over loss and damage, the United States and European Union somewhat softened their position by agreeing to discuss the issue at COP27.
European Commission Vice President Frans Timmermans said the EU was open to the creation of a funding facility but that it should be among a "mosaic" of options that include existing financial instruments.
"We will do everything to find consensus," he said, adding however that he expects "quite a long and difficult journey to the end of this process".
"If this COP fails we all lose and we have absolutely no time to lose," he told journalists.
Protests held within the conference compound have sought to keep up the pressure on delegates, with small but vocal crowds of demonstrators chanting: "What do we want? Climate justice!"
Timmermans took issue with the G77+China proposal as it limits the donor base for a fund to a list of two-dozen rich nations drawn up in 1992.
The top EU official has pointed out that some countries, notably China, would be left "off the hook" from contributing to the fund even though they have grown wealthier since 1992.
"I'm still hopeful that we can reach an agreement on this, but then I do ask of our partners to make sure that it's fair so that everybody who is in a position to contribute contributes," Timmermans said.
Pakistan's climate minister Sherry Rehman, whose country chairs the G77+China, said the group was still "seeking to find common ground even at this late hour".
Rehman suggested that concerns from rich countries about liability could be addressed.
"For countries worried or anxious about liabilities and judicial proceedings, I think we can work around all those anxieties," she said.
Rehman recalled that Pakistan was devastated by floods this year that cost the country $30 billion.
"Vulnerability should not become a death sentence," she said.
"We are the ground zero of climate change," she added. "We must convey a message of hope to all those people that have pinned their ambitions on this particular COP."
Guterres called for progress across the board on the goal of limiting warming to 1.5 degrees Celsius compared to preindustrial levels.
Rich nations should also finally deliver on their unmet pledge to provide $100 billion a year since 2020 to help the developing world green their economies and adapt to future impacts, and make progress on future financing.
Observers at the talks said loss and damage could be make-or-break for COP27.
"This is the issue around which the entire (COP)27 package hinges," said Tom Evans, an expert on climate diplomacy at think tank E3G.
Laurence Tubiana, a main architect of the 2015 Paris Agreement as France's top negotiator, told AFP a "possible landing zone for a compromise is not yet in view."
"Things could really go off the rails at the end."