By Alister Doyle, Environment Correspondent

OSLO (Reuters) - A thaw of the Arctic icecap is accelerating because of global warming but nations in the region including the United States are deadlocked about how to stop it.

Due for publication on Nov. 8, an eight-nation report compiled by 250 scientists says the Arctic is warming almost twice as fast as the rest of the planet due to a buildup of heat-trapping gases and the trend is set to continue.

" We are taking a risk with the global climate," said Paal Prestrud, vice-chair of the Arctic Climate Impact Assessment (ACIA) report, which says emissions of gases from cars, factories and power plants are mostly to blame.

The Arctic icecap has shrunk by 15-20 percent in the past 30 years and the contraction is likely to accelerate, Prestrud said. The Arctic Ocean could be almost ice-free in summer by the end of the century.

Inuit hunters are falling through ice, permafrost is thawing and destabilizing foundations of buildings and vital winter roads while the habitat of creatures from polar bears to seals is literally melting away.

The report says that the thaw will have some positive side-effects. Oil and gas deposits will be easier to reach, more farming may be possible and short-cut trans-Arctic shipping lanes may open.

NATIONS SPLIT

Diplomats said governments in nations around the Arctic rim -- the United States, Russia, Canada, Denmark, Norway, Sweden, Finland and Iceland -- disagree about what to do, with the United States most opposed to any drastic action.

Arctic nations are meant to agree policy recommendations based on the report at a meeting of foreign ministers in Iceland on Nov. 24.

" U.S. negotiators say ' we already have a policy on global warming -- we can' t have a new one just for the Arctic' ," one European diplomat said. Government negotiators will try to break deadlock with a new round of talks in mid-November.

President Bush (news - web sites) pulled out of the U.N.' s Kyoto protocol on global warming in 2001, arguing it was too expensive and wrongly excluded developing nations.

The other Arctic nations, most recently Russia, have agreed to Kyoto' s target of cutting developed nations' emissions of carbon dioxide by five percent below 1990 levels by 2008-12.

The WWF environmental group Tuesday accused the eight nations, which account for 30 percent of global greenhouse gas emissions, of hypocrisy in sponsoring the Arctic report while failing to crack down.

" The big melt has begun," Jennifer Morgan, director of the WWF' s global climate change campaign, said in a statement. She said industrialized nations were using the Arctic as a guinea pig in an uncontrolled experiment on climate change.

Scientists have agreed to discuss parts of the report ahead of full publication -- Reuters published main conclusions in September. Some European governments originally wanted the report issued before Tuesday' s U.S. presidential election.

The report projects that temperatures in the Arctic will rise by 4 to 7 degrees Celsius (8 to 14 degrees Fahrenheit) in the next 100 years. If temperatures then stayed stable, the Greenland icecap would melt altogether in 1,000 years and raise global sea levels by about seven meters (23 ft).

The thaw of the icecap floating on the Arctic Ocean does not affect sea levels, in the same way that a full glass of water with an ice cube jutting above the brim does not spill when the ice melts since ice takes up more space than water.