Chief negotiators last night remained optimistic that a new international deal on climate change can be hammered out in the final hours of United Nations talks in Paris.
They said a few “red line issues” are all that stand in the way.
“We’re now down to some of the so-called red line issues, some of the defining issues in the convention that have to do with principles,” said Achim Steiner, United Nations environment program director.
He said this should offer “courage and hope that we are actually moving to an agreement”.
As negotiations continue, sharp divisions remain on key measures in the agreement, which aims to avoid dangerous climate change and provide finance for poor countries to deal with the impacts of global warming.
More than 180 countries have presented emissions targets for after 2020, when the proposed accord is scheduled to take effect.
But scientific analyses show ambitions will not be enough to limit global warming to 2C above pre-industrial times, the overarching goal of the summit.
Many countries have recently backed revising the target down to 1.5C, but current pledges for action up to 2030 put the world on a path to almost 3C of warming by the end of the century.
A draft of the text released on Wednesday contained the potential for ambitious targets on curbing rising global temperatures and cutting emissions over coming decades, as well as weaker options.
But European leaders claim any deal is meaningless if countries cannot reassess and ramp up their climate actions.
A “high ambition coalition” of countries spanning the EU, including the UK, some of the world’s poorest countries and the US, are calling for a robust “review and ratchet” mechanism that would see countries re-examining and raising their level of pledged action if necessary every five years.
European climate action and energy commissioner Miguel Arias Canete said: “You can have a very ambitious long-term goal but unless you come back every five years to update your targets you can never meet your long-term goal.”
A number of countries, including Malaysia and China, are thought to be pushing back against a review system.
International migration experts said the deal must also address the growing problem of climate refugees, forced to flee extreme weather.
Differences in responsibilities between countries also remain a thorny issue in discussions.