Just three days before world leaders are expected at the table to seal a UN climate pact, ministers in Copenhagen were struggling to break deadlock that threatens to derail the whole process.
Organizers of the talks said environment ministers would work deep into night to narrow wide differences, saying the bulk of the work must be complete before some 130 leaders formally join the Dec 7-18 meeting on Thursday.
"We have seen significant progress in a number of areas but
U.N. climate chief Yvo de Boer said there had been significant progress in several areas, "but we haven't seen enough of it...We are in a very important phase."
Danish president of the talks Connie Hedegaard urged swifter progress, likening the climax of the two-year talks to a looming school exam. "It's just like schoolchildren. If they have a very long deadline to deliver an exercise they wait for the last moment," she said.
Talks remained stalled after a stand-off the previous day, held up by disputes over the level of emissions cuts by rich countries and a long-term global target to curb a rise in global temperatures which could trigger rising sea levels, floods and drought.
German Chancellor Angela Merkel told reporters in Berlin that she was "a bit nervous" about the lack of progress.
"There's a great deal yet to do, the parties are quite far apart on a fair number of issues," said Todd Stern, U.S. special envoy for climate change, adding he did not expect any change in U.S. targets for emission curbs during the talks.
Business leaders say they want a clear deal with short and long-term targets so that they can invest appropriately.
"There are still lots of issues that will likely be discussed only at the ministerial level, and that gives us some cause for concern," said Abyd Karmali, global head of emissions trading at Bank of America Merrill Lynch.
Major U.S. businesses including Duke Energy, Microsoft and Dow Chemical called for tough U.S. emissions cuts which would mobilize a shift to a greener economy.
Draft texts dated Tuesday showed that national negotiators had stripped out figures for long-term global goals and rich nation emissions cuts by 2020 from last week's U.N. texts. The numbers could be re-inserted if agreement is reached.
India's environment minister Jairam Ramesh told Reuters that the talks could even break down on "serious" outstanding issues.
"There is confusion and lack of clarity at this stage." "There could be breakdown on many issues."
Brazil's climate change ambassador Sergio Serra was more upbeat -- "You can have a breakthrough ... with the pressure of time and of public opinion ," he told Reuters.
Ministers expected to work late into the night. "It's very clear that ministers have to be extremely busy and focused over the next 48 hours if we are going to make the success we are trying to make," said Hedegaard.
"It is not their (leaders') role to negotiate text," said Serra, emphasizing that most work must be done by Thursday.
The Copenhagen talks have stumbled over a long-running rich-poor rift on addressing the threat of climate change.
A "BASIC" group of China, India, Brazil and South Africa was "coordinating positions, almost on an hourly basis," India's Ramesh said, reinforcing the entrenched rich-poor positions.
South African Environment Minister Buyelwa Sonjica, speaking for the group, said pledges by developed nations for emissions cuts were "less than ambitious and ... inconsistent with the science."
Developing nations also want the industrialized world to pay poorer countries to prepare for and slow climate change.
Japan would offer $10 billion in aid over three years to 2012 to help developing countries fight global warming, including steps to protect biodiversity, a Japanese newspaper said on Tuesday. The European Union has offered a similar sum.
French President Nicolas Sarkozy said in Paris that he hoped U.S. President Barack Obama supported "fast start" aid. "President Obama often speaks about his links with Africa, it is time to show it," he said.
Most developed countries support interim climate funds of about $30 billion from 2010-2012 to help poorer nations, many of which say that's not enough.
Another thorny issue was how far developing nations should be bound to targets to slow their growth in emissions, a process known as measurement, reporting and verification (MRV).
"The MRV issue is a very serious divider," said India's Ramesh. The issue "might not sound that sexy but its still a very crucial part because that is where there are red lines to different parties," said Hedegaard.