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.
Developed nations, which promised in 2009 to raise climate aid to $100 billion a year after 2020 from $10 billion a year in the period 2010-12, were resisting calls by the developing world to set targets for 2013-19.
A draft text merely urged developed nations, which have been more focused on spurring economic growth than on fixing climate change, to set "increasing levels" of aid.
It also suggested they report every two years on their approaches to stepping up finance levels to $100 billion.
A group of developing countries and China were in favour of an amendment to the text that "at least $70 billion" a year of climate finance is committed from 2016.
Overtime
The talks have also proposed a new "Warsaw Mechanism" which would provide expertise, and possibly aid, to help developing nations cope with loss and damage from extreme events such as heat waves, droughts and floods, and creeping threats such as rising sea levels and desertification.
Developing nations have insisted on a "mechanism" - to show it was separate from existing structures - even though rich countries say that it will not get new funds beyond the planned $100 billion a year from 2020.
Many delegates also said they wanted a clearer understanding of when nations will publish their plans for long-term cuts in greenhouse gases in the run-up to a summit in Paris in 2015.
A text on Saturday said that all nations should "initiate or intensify" their domestic preparations for "intended nationally determined commitments" and have them ready by the end of the first quarter of 2015, if they could.
The United States is among those advocating pledges be made by the end of the first quarter of 2015. The European Union is among countries which want pledges in 2014.
"It's not everything we wanted, but we know there are some issues we cannot solve here," Pete Betts, lead negotiator for the European Union, told delegates.
Meanwhile, many developing nations want to see more urgency. Typhoon Haiyan in the Philippines, which has killed over 5,000 people, has put the spotlight on extreme weather.
In September, a UN panel of scientists raised the probability that most climate change since 1950 is man-made to at least 95 percent, from 90 in a previous assessment in 2007.
It also said that "sustained and substantial" cuts in greenhouse gases were needed to achieve a UN goal of limiting warming to manageable levels.
"We have compromised on many issues, but there is a limit for compromise by the most vulnerable countries of this planet," said Nepal's Prakash Mathema, chair of the group of least developed countries.
