World climate talks in Bali have gone into their last scheduled day amid fierce disagreement over targets for cutting greenhouse gas emissions.
If global temperatures rise, billions will face water shortages
EU ministers have warned they will boycott a US-led climate summit next month unless the Bush administration backs firm targets for emissions cuts.
The US favours allowing governments to set voluntary targets.
Indonesia is trying to broker a compromise that would remove firm targets from the final text.
The proposal would remove reference to a numerical target for emissions cuts by 2020, but would maintain a longer-term ambition of more than halving emissions by 2050.
Delegates spoke of some progress behind the scenes.
"We are entering the final hours of the conference ,and I'm pleased to say there has been progress both towards the 'Bali roadmap' and some other important issues," said the EU's Environment Commissioner Stavros Dimas.
The Bali roadmap is the document supposed to emerge from this conference, which would outline the parameters for negotiating a successor to the Kyoto Protocol, whose current emissions targets expire in 2012.
'Don't give up'
European Union states and their allies want industrialised countries to agree to cuts of 25%-40% in greenhouse gas emissions - which mainly come from burning fossil fuels - from 1990 levels by 2020.
That target would not apply to developing countries. Instead an "indicative emissions reductions range" would be included in the plan, Mr Dimas said.
On the other side are the US, Canada and Japan. The US in particular, which has not ratified the Kyoto agreement, says any numerical agreement would prejudge the outcome of future talks.
The US delegation in Bali has come under widespread criticism from environmental advocates, with some suggesting the US position was below even the minimum of expectations for the conference.
US officials remained largely tight-lipped as negotiations resumed on Friday morning.
However, Paula Dobriansky, the head of the US delegation, said she was committed to obtaining an "environmentally effective and economically sustainable" agreement by 2009.
"We are working very hard to achieve consensus," the New York Times reported her as saying.
Among those criticising the US was Nobel laureate and former Vice-President Al Gore, who spoke to a packed hall on Thursday.
Mr Gore won loud applause from delegates as he said: "My own country, the United States, is principally responsible for obstructing progress in Bali."
But the Nobel Peace Prize laureate also urged delegates not to give up, reminding delegates that the US presidential election in 2008 could herald a new approach in Washington.
"Over the next two years the United States is going to be somewhere it is not now. You must anticipate that," he said.
The US is the world's biggest emitter of greenhouse gases, and most parties recognise that climate change talks without it would be meaningless.
In September the US hosted the inaugural summit of the "major economies" or "big emitters" group, which brings together 16 of the leading greenhouse gas producing countries.
The US is due to host a second summit next month in Honolulu.
The BBC's environment analyst Roger Harrabin, reporting from Bali, says the European threat to boycott the conference pushes President Bush into a corner.
Either he agrees to negotiate big cuts, or he has to explain to an increasingly concerned American public why Europe is boycotting a meeting which the president himself has invented and championed, our correspondent says.