Nearly 200 countries haggling over how to stop climate change - and how to pay for it - failed to reach a deal on schedule on Friday, setting the stage for the wrangling to continue late into the night.
The two-week UN conference in Doha was never meant to yield a global climate pact to curb emissions of greenhouse gases - that has been put off until 2015.
But negotiators struggled to agree even on more modest issues, including how to scale up money to help poor countries cope with global warming, and finalising the extension of an existing treaty that only covers about 15% of global emissions.
The US and other developed countries rejected a draft agreement put on the table on Friday. Several developing countries also said they could not accept the wording of some paragraphs, highlighting the deep divide that has haunted the talks since they first started two decades ago.
One of the key disagreements was over money. Poor countries want firm commitments from rich nations to scale up climate aid for them to 100 billion US dollars (£62 billion) annually by 2020, a general pledge that was made three years ago. But rich nations are unwilling to commit to specific targets now, citing world financial turmoil and pressure on their budgets.
The financing issue has overshadowed the talks since they started last week in Qatar, the first Middle Eastern country to host the slow-moving annual negotiations aimed at crafting a global response to climate change.
Rich nations pledged in 2009 to deliver long-term financing to help poor nations switch to clean energy and adapt to rising sea levels and other impacts of global warming. They offered 10 billion dollars (£6.2 billion) a year in 2010-2012 in "fast-start" financing, pledging that the amount would be increased to 100 billion dollars in 2020. But they did not say how.
A draft text early on Friday urged developed countries "to make firm commitments to provide scaled up climate finance beyond 2012" but did not include any mid-term targets. Gambia delegate Pa Ousman Jarju, representing the least developed countries, said they were still insisting on a mid-term financing target but "we have not reached a stage where we would walk out".
Negotiators were also trying to finalise an agreement to formally extend the Kyoto Protocol, an emissions reduction pact for rich countries that expires at the end of this year. One of the sticking points was whether to allow countries to carry over surplus emissions allowances into the next phase. The US never joined Kyoto while Japan, New Zealand, Canada and Russia do not want to be part of the extension, meaning it would only cover about 15% of the world's emissions of greenhouse gases.
Governments have set a deadline of 2015 to agree on a wider deal that would include both developed and developing countries, which now produce a majority of the world's emissions. The goal of the UN talks is to keep temperatures from rising more than 2C, compared with pre-industrial times. Temperatures have already risen about 0.8C above that level, according to the latest report by the UN's top climate body. A recent projection by the World Bank showed temperatures are on track to rise by up to 4C by the year 2100.