But the global attention it could draw to the cause of some of the world's smallest and lowest-lying countries, which fear they could cease to exist if sea levels rise as global temperatures increase, may alone justify the attempt.

"We are facing a situation that can cause unparalleled destruction and displacement of people in the Pacific," said Stanley Simpson of the Fiji-based regional pressure group Pacific Concerns Resource Centre.

"It (a court case) would be very difficult. But even if they lose the case, we believe they will win it in the court of public opinion," he told Reuters.

Tuvalu's Prime Minister Koloa Talake said over the weekend that his nation of 10,000 people was considering suing the United States and Australia over their failure to ratify the 1997 Kyoto protocol on cutting greenhouse gas emissions.

The David versus Goliath proposal is barely off the drawing board and it is not clear who would be sued or where.

Tuvalu, a string of nine coral atolls five metres (16 feet) above sea level at their highest point, says its last palm tree could sink beneath the aquamarine waters within 50 years.

Last year it appealed to South Pacific heavyweights Australia and New Zealand to give its people special visas in case they became "environmental refugees," forced to flee. It was rebuffed.

Prime Minister John Howard has defended Australia's reluctance to ratify the Kyoto agreement, saying it served little purpose if it was not backed by the world's top polluter, the United States, and did not include developing nations.

Some scientists remain sceptical about global warming. But the U.N.'s Intergovernmental Panel on Climate Change predicts sea levels will rise by up to 0.88 metres by 2100, as ice caps and glaciers melt, and increasing temperatures cause water to expand.

ISLANDS IN FIRING LINE

In the firing line are low-lying coral atolls and islands, like the Maldives in the Indian Ocean, and Tuvalu, Kiribati, Niue and the Marshall Islands in the Pacific.

Clive Hamilton, head of the Australia Institute think-tank, said Australia was vulnerable and had to brace itself for years of possible litigation as the country with the highest per capita emissions of greenhouse gases in the world.

"Tuvalu is doing no more than applying a basic principle of law - if someone does you harm, then you should be able to stop the aggressor from harming you and seek restitution," he said.

Rosemary Rayfuse, an international law expert at the University of New South Wales, said Australia and the United States could possibly be challenged in the International Court of Justice for not ratifying Kyoto, an accord both had signed.

International principles dictate that countries undertake not to injure other nations by actions in their own territories.

But the international court normally requires the target to agree to be sued, a highly unlikely scenario in this case.

An alternative avenue might be the U.S. alien tort claims act, which could allow Pacific islands to sue car makers, power station operators or oil firms for pollution.

The costs of a law suit would be prohibitive for a place like Tuvalu, which has annual economic output of just $12 million.

"You're talking lots and lots of dosh," Rayfuse added. "Where are are they going to get the money from?"

But Tuvalu has friends.

Pressure groups such as Greenpeace have been studying the courts as a tool against climate change for around two years and there has been talk of adopting Tuvalu as a cause celebre.

"They (the United States and Australia) are clearly not listening to either the scientific evidence or reason," said Frances MacGuire, Greenpeace's Pacific climate campaigner.