When head of the United Nations climate secretariat entered the press hall at the Copenhagen climate conference on Tuesday evening, he was carrying a life ring, which he had just been handed by the development NGO Oxfam. “Act now. Save lives,” it said on the ring. And a photographer asked him to stick his head through the ring for a picture. Yvo de Boer grinned.

“I'll hang myself with it if this here goes wrong,” he replied. “This here.” Yvo de Boer was referring to the climate summit, and it reached a critical phase on Tuesday. "In the next 48 hours, the environment ministers are going to have to work very hard,” de Boer said. The fact is that with just three days of negotiations remaining at the climate change summit in Copenhagen, fears are growing that the conference could end in failure.

On Wednesday afternoon, according to delegates at the conference, the Danish conference chair is to present the first official draft of the closing statement. But on Tuesday, it was more unclear than ever just how binding the statement might be. The US delegation dashed the hopes of leftover optimists with its announcement that President Barack Obama would not be improving the earlier American pledge to cut greenhouse gas emissions by 17 per cent by 2020 relative to 2005. Likewise, referring to his country's stated emission reduction targets, China's climate ambassador Yu Qingtai said: “We announced those targets, we don't intend to put them up for discussion.”

China accused the US and other rich countries of having offered less at the conference this week rather than more. Some representatives, particularly those from island nations threatened directly by climate change, said they would not sign a “suicide pact.” The offers currently add up to a reduction of CO2 output among industrialised nations by 16 to 23 per cent by 2020 relative to the baseline year of 1990. The US offer of a reduction of 17 per cent relative to 2005 is merely a small drop in the bucket. If one calculates the offer using the baseline year of 1990, it represents a mere 4 per cent cut (which is less than what binding countries in Kyoto Protocol have pledged, which is a 5 per cent reduction below 1990 levels).

Countries such as China and India, on the other hand, have merely promised to cut their "carbon intensity", which means the amount of CO2 emitted for each dollar of economic activity. They refuse to commit to any absolute reduction targets with good reason, Rajendra Pachauri, head of the intergovernmental panel on climate change, told Speigel Online. “It is not fair to speak about reductions for a country in which 400 million people have no access to electricity and 90 per cent of the rural population burn twigs, leaves, cow dung and agricultural residue for cooking barely two meals a day,” he said. “Politically, one can forget about cuts for India." He said were the Indian government to commit to any cuts at Copenhagen, it would collapse soon after arriving in Delhi.

An unofficial draft of the concluding statement, which circulated at the summit on Tuesday, was correspondingly weak. There were no numbers at all attached to any of the central questions being addressed by the summit: by how much CO2 emissions will be reduced on the long term; when will the peak be reached; what the maximum acceptable temperature increase will be; how much help will the developing world receive from rich nations. Everything remained open.

If there are no answers to those questions by the time the conference ends on Friday, the failure will be complete. “The industrial countries have to present a collective reduction target -- not for 2050 but for 2020,” Pachauri said, commenting on the current lack of urgency. If that does not happen, there will be “big problems in some countries of the world,” he said, referring specifically to African nations and island states.

The task for the next few days remains huge given the gulf between the interests of the nations involved. Oil-producing states fear for their economic future, small island states for their actual existence. And, thanks to the principle of unanimity, every single of the 192 governments represented at the summit could provide a conclusive closing statement. “This is a United Nations conference,” says the Danish conference head Connie Hedegaard. “Everyone must agree to everything.”