UN Secretary General Antonio Guterres described a major climate change summit in Madrid as "disappointing" as the nearly 200 countries present failed to agree on concrete steps to fight global warming.
A declaration from the two-week long Cop25 underlined "the urgent need" for carbon-cutting measures but fighting among those attending meant nothing substantial was decided.
In the formal talks, European governments, small island states and the poorest nations struggled to persuade big-emitting countries, from the US and Brazil to India, China and Japan, to commit in 2020 to making their action plans more ambitious.
Cop25 has become mired in arguments over potential loopholes in rules governing international carbon trading, favoured by wealthier countries to reduce the cost of cutting emissions.
"I am disappointed with the results of Cop25," Mr Guterres said. "The international community lost an important opportunity to show increased ambition on mitigation, adaptation and finance to tackle the climate crisis."
Activists had earlier hit out at the inertia in the Madrid talks.
Meetings dragged on until the early hours of Sunday as representatives from the countries failed to agree on crucial matters that marked two weeks of talks dominated by points of difference.
"Today the citizens of the world are asking for us to move ahead faster and better, in financing, adaptation, mitigation," said Carolina Schmidt, Chilean Environment Minister and President of Cop25.
Genuine ambition in how far each country was willing to cut carbon emissions or assist less wealthy peers to do so largely failed.
"The climate emergency is now," said Oumarou Ibrahim from the Chad Mbororo community, which relies on agriculture. "We need our voices to be here. Action must start now."
Africa’s Sahel region has been beset by droughts and floods that have meant small crops and herders running out of grazing areas.
"From fires and power shut-offs in California to floods and other disasters, disabled people are the first to be left behind and the first to die," said disability rights campaigner Jason Boberg, from New Zealand.
Ms Schmidt admitted “this has been very tough, very long” in reference to the two weeks of talks, but she insisted “things are coming together”.
"We are almost there. It's hard, it's difficult, but it's worth it," she added.
But the UN climate meetings, informally known as Cop25, were decried by Alden Meyer, a climate expert.
“I've been attending these climate negotiations since they first started in 1991, but never have I seen the almost total disconnection we've seen here in Madrid between what the science requires and the people of the world demand, and what the climate negotiators are delivering,” Mr Meyer said.
“The planet is on fire and our window of escape is getting harder and harder to reach the longer we fail to act."
Draft agreements circulated overnight on Saturday risked undoing or stalling on commitments made in the 2015 Paris climate accord.
Among the main issues being discussed in Madrid are rules for international carbon markets and a system for channelling money to help poor countries cope with the economic impact of climate change.
The Paris agreement, from which President Donald Trump has begun withdrawing the US, was a global action plan that aimed to keep global temperature rises to a minimum.
It was critical for countries to resist attempts by Brazil and others to keep large piles of carbon credits amassed under a now-discredited system, Nathaniel Keohane, of the Environmental Defence Fund, told AP.
“That opens up a potentially major hole in the fabric of the Paris Agreement,” Mr Keohane said. “There is really a question of integrity at stake and it is really critical for countries to hold the line.”
Kevin Conrad, Papua New Guinea’s climate envoy, told the Madrid audience that "over the last 24 hours, 90 per cent of the participants have not been involved in this process".
The talks were originally supposed to be held in Chile but mass demonstrations forced them to be moved abroad.