Global talks on launching a new offensive against climate change went down to the wire Friday, mired in bitter rows over how far industrialised countries would commit to curbing greenhouse gas pollution.
A noon (0400 GMT) goal sketched by organisers for concluding the conference expired amid the stalemate, as host Indonesia battled to bridge a gap between the United States on one side and the European Union and developing countries on the other.
Green groups accused Washington of seeking to sabotage the crucial meeting on the Indonesian resort island of Bali.
The United States "is behaving like passengers in first class on a jumbo jet, who believe that a catastrophe in economy class will not affect them," Tony Juniper of Friends of the Earth International.
"The reality is however very different -- if we go down, we go down together, and the United States needs to know that very quickly."
The 12-day marathon was officially due to close at 6:00pm (1000 GMT), but the head of the UN Framework Convention on Climate Change had urged parties to finish their wrangling by noon.
"Time is running out for other developed countries to live up to their responsibilities," said European Environment Commissioner Stavros Dimas.
"I hope they will do so in the coming hours so that Bali goes down in history as a successful start to a new global agreement that will tackle the vital challenge of climate change."
Nobel-winning UN scientists this year painted their grimmest tableau yet about the "greenhouse effect" in which dangerous, invisible gases spewed from fossil fuels act like an atmospheric blanket, stoking up heat from the Sun.
This is causing Earth's delicate climate system to change, and the impact could be catastrophic for millions of people just decades from now, they say.
The aim of the conference is not to draw up a new pact per se, but to launch negotiations toward such a deal.
It would take effect after 2012, when the current provisions of the Kyoto Protocol -- a landmark pact requiring industrialised nations to meet a ceiling on their greenhouse gas emissions -- expire.
The world's two biggest carbon polluters, the United States and China, together account for about half of all emissions, but lie outside the Kyoto curbs.
The United States rejected Kyoto in 2001, although it remains part of the overall UN process, while China, as a developing nation, does not have binding emissions targets.
The biggest stumbling block in Bali has been over whether the text should include figures indicating how far industrialised countries are willing to cut emissions to meet scientists' appeals for drastic, early reductions.
The figures sketched are cuts of 25-40 percent by 2020 compared with 1990 levels, which the European Union and emerging countries say are essential as a show of goodwill from the countries historically most to blame for warming.
But the United States is against any move that, it suspects, would haul it down the path toward Kyoto-style emissions curbs.
Delegation sources said Japan, Canada and Russia backed the US line, with Australia's new government, which ratified Kyoto as its first act in office, yet to clarify its stance.
Indonesia tried to bridge the gap by scrapping the 25-40 figure but setting a goal of having greenhouse gases peak "in the next 10 to 15 years" and then fall to well below half of 2000 levels by 2050.
That idea incensed developing countries and the EU, delegates said.
"If the industrialised countries... are not ambitious enough, then the developing countries will also weaken their own proposals, so it's going down and not up," German Environment Minister Sigmar Gabriel said.
"We are searching for opportunities to strengthen the text."
In an overnight move, US negotiators proposed text that would effectively give any country the right to take voluntary action rather than be brought into mandatory curbs, green groups said.
On Thursday, new Nobel peace laureate Al Gore blasted US tactics and urged the rest of the world to sidestep Washington."