Sleep-starved envoys charged with saving mankind from catastrophic climate change aim to wrap up a historic Paris accord on Saturday (local time) after battling through a second all-night session of UN talks.
Eleven days of bruising international diplomacy in the French capital appeared to finally open the door to an elusive deal, now expected to be delivered one day after the original Friday evening deadline.
"It will be presented Saturday morning for adoption midday," said a source at the French presidency of the climate talks, an annual gathering that frequently misses deadlines by days.
"Things are moving in the right direction," said French Foreign Minister Laurent Fabius, who is presiding over the talks, according to the source who spoke to AFP.
Releasing a fresh draft of the pact on Thursday night that showed progress on some key issues, an increasingly confident Fabius had said a deal was "extremely close".
Fabius instructed the ministers from 195 nations to make unprecedented compromises on the outstanding issues: extremely complex rows primarily pitting rich countries against poor that have derailed previous UN efforts.
World leaders have described the Paris talks as the last chance to avert disastrous climate change: increasingly severe drought, floods and storms, as well as rising seas that engulf islands and populated coastal regions.
The planned accord would seek to revolutionise the world's energy system by cutting back or potentially eliminating the burning of coal, oil and gas, which leads to the release of Earth-warming greenhouse gases.
UN efforts dating back to the 1990s have failed to reach a truly universal pact to contain climate change.
Developing nations have insisted established economic powerhouses must shoulder the lion's share of responsibility as they have emitted most of the greenhouse gases since the Industrial Revolution.
But the United States and other rich nations say emerging giants must also do more, arguing that developing countries now account for most of today's emissions and thus will be largely responsible for future warming.
They are arguments worth hundreds of billions of dollars, which still need to be resolved before the negotiators can leave Paris.
Among the most striking developments in the latest draft of the agreement is wording that seeks to resolve a dispute over what temperature limit target to set.
Nations most vulnerable to climate change had lobbied hard to limit warming to no more than 1.5degC compared with pre-Industrial Revolution levels.
However several big polluters, such as China and India, had preferred a ceiling of 2degC, which would allow them to burn fossil fuels for longer.
The latest draft offers a compromise that states the purpose of the agreement is to hold temperatures to well below 2degC, but to aim for 1.5degC.
"With this, I would be able to go home and tell my people that our chance for survival is not lost," said Tony de Brum, Foreign Affairs Minister of the Marshall Islands, one of the archipelagic nations that could be wiped out by rising sea levels.
Another key set of words the French hosts hope have been settled in the draft is a commitment for all nations to aim for "the peaking of greenhouse gases as soon as possible".
"Assuming the deal does go through, this will be the first time in history at which virtually every country has committed to restraining its emissions of greenhouse gases," said Richard Black, director of the London-based Energy and Climate Intelligence Unit.
Australian Foreign Minister Julie Bishop also told reporters after the draft was released that: "There's a sense of optimism".