A UN climate summit is at risk of collapsing today after all-night negotiations between countries left them more divided than ever over on how to fight global warming and pay for its ravages, having already gone into overtime for the talks.

Delegates from across the world have been in Madrid for the COP 25 conference for nearly two weeks attempting to work towards a deal for countries to commit to new carbon emissions cuts by the end of 2020.

Diplomats from rich nations, emerging giants and the world's poorest countries - each for their own reasons - found fault in a draft agreement put forward by meeting host Chile in a botched attempt to strike common ground.

The South American country was meant to host the event but billionaire President Sebastian Pinera cancelled the hosting plans as well as an Asia-Pacific APEC economic summit in November due to protests.

Faced with five-alarm warnings from science, deadly extreme weather made worse by climate change, and weekly strikes by millions of young people, negotiations in Madrid were under pressure to send a clear signal that governments are willing to double down in tackling the crisis.

A delegate at the COP25 climate talks in Madrid relaxes on a sofa as the talks between countries risk collapse over commitments to cutting carbon emissions by the end of 2020

Swedish climate activist Greta Thunberg addressed a plenary of U.N. climate conference during with a meeting with leading climate scientists at the COP25 summit in Madrid, Spain

Activists from climate groups as well as school children gather to protest outside the venue of the U.N. Climate Change Conference in Madrid

But the 12-day talks, now deep into overtime, had retreated even further from this goal on Saturday.

'It appears that we are going backwards on the issue of ambition when we should be calling for a quantum leap in the other direction,' Marshall Islands climate envoy Tina Stege said.

'I need to go home and look my children in the eye and say we got an outcome that is going to ensure their future, and the future of all of our children,' she added, a catch in her voice.

Veteran observers of UN climate talks were stunned by the state of play nearly 24 hours after the negotiations had been set to close.

'I have never seen such a disconnect between what the science requires and the people of the world demand, versus what the climate negotiations are delivering,' said Alden Meyer, strategy and policy director at the Union of Concerned Scientists.

Green activists dumped horse manure and staged a mock hanging outside the venue of a U.N. climate summit in Madrid on Saturday, airing their frustration at the failure of world leaders to take meaningful action against global warming

In contrast to a protest held last weekend, in which hundreds of demonstrators blocked one of Madrid’s central shopping streets for a mass disco-dance, the mood at the gathering was subdued

Twelve members of the group stood on melting blocks of ice, nooses drawn tight around their necks to symbolise the 12 months remaining until the next summit, when the Paris deal enters a make-or-break implementation phase

Oxfam has accused world leaders of ignoring the threat posed by climate change

Outside the exhibition centre, activists from Extinction Rebellion dumped horse manure as they staged a protest alongside an international movement of school children demanding faster and more tougher action.

Under the Paris accord, countries agreed in 2015 to work to limit global temperature rises to 'well below' two degrees Celsius through a series of voluntary action pledges that step up over time.

'The one thing in Paris that gave us hope was that the deal is going to be strengthened over time,' said Mohamed Adow, Director of Power Shift Africa, referring to the 196-nation Paris climate treaty.

'If that doesn't come through, Madrid will have failed.'

The push for a strengthening of voluntary carbon cutting plans is led by small-island and least-developed states, along with the European Union.

Demonstrators dressed in costumes protested as the talks inside faced collapse

The United Nations Secretary-General has warned that failure to tackle global warming could result in economic disaster

Ministers from this 'high ambition coalition' have called out countries they see as blocking a consensus call for all countries to step up, notably the United States, Australia and Saudi Arabia.

China and India, the world's No. 1 and No. 4 carbon emitters, meanwhile, have made it clear they see no need to improve on their current emissions reduction plans, which run to 2030.

These emerging giants have chosen instead to emphasise the historical responsibility of rich nations to lead the way and provide financing to poor countries.

The COP 25 summit was also meant to finalise a chapter on carbon markets in the Paris rulebook, which goes into effect next year.

But a complicated wrangle over how to structure markets, and deal with carbon credits left over from the Kyoto Protocol, which expires at the end of 2020, have remained deadlocked, and may be punted to further talks next year.

The COP 25 summit was also meant to finalise a chapter on carbon markets in the Paris rulebook, which goes into effect next year

The United States, which is leaving the landmark Paris climate deal next year, was accused of acting as a spoiler on a number of issues vital to climate-vulnerable nations.

This included so-called 'loss and damage' funding to help disaster-hit countries repair and rebuild.

'The US has not come here in good faith,' said Harjeet Singh, climate lead with charity ActionAid.

'They continue to block the world's efforts to help people whose lives have been turned upside down by climate change.'

Even if nations in Madrid snatch victory from the jaws of defeat and agree to implement their pledges, Earth is on course to warm more than 3C by 2100.

'If there was one time in the history when I would say governments fucked up, I would say today in Madrid, governments fucked up,' said Mohamed Adow, Director of Power Shift Africa.

'People across the world must rise to save the planet.'