Talks to lay the foundations for a new UN climate pact due in 2015 were deadlocked as they ran into overtime on Saturday, with nations at odds over stepping up finance for developing countries to ease the impact of global warming.
The Warsaw meeting, which had been due to end on Friday, was meant to lay the groundwork for creating the first climate accord to be applicable to all nations by 2015, which would come into force after 2020.
However the only concrete measure to have emerged was an agreement on new rules to protect tropical forests, which soak up carbon dioxide as they grow.
Nearly 200 countries assembled at the UN conference have stumbled over three major issues over the past two weeks: the level of emissions cuts, climate finance and a "mechanism" to help poor countries deal with loss and damage from global warming.
"Climate change talks are still on knife edge after a long night. A few countries (are) insisting on looking backwards. Could be a long day," British Energy and Climate Change Minister Edward Davey said on Twitter.