The tsunamis, or huge waves, caused by an undersea earthquake in southeast Asia on December 26 have highlighted the extreme vulnerability of the world's smallest countries, some 40 of which will be represented at next week's talks.

The Maldives, a cluster of 1,192 low-lying islands scattered across the Indian Ocean, saw several of them entirely destroyed by the giant waves spreading out from the quake zone.

Looking beyond natural catastrophes to the broader challenge of global warming, the January 10-14 United Nations conference aims to help small island states prepare for the future as the world's oceans steadily rise.

Around the world, thousands of islands, river deltas and low-lying coastal areas, already at constant risk of being swamped by violent storms and high tides, are set to face a growing battle against the encroaching seas.

Average sea levels have increased by 10 to 20 centimetres (four to eight inches) over the past century, and are expected to rise by a further nine to 88 centimetres (four inches to three feet) by the year 2100, as global warming causes glaciers and polar ice caps to melt.

As many as 200 million people could be forced to migrate by the end of the century, as their homelands are swallowed up by the waters, according to a 2001 report by a group of UN climate experts working on the basis of population growth estimates of the time.

With adequate protection systems in place, however, systems capable of fending off both the ocean's gradual rise and storm-driven floods, experts believe the number of displaced could be halved to 100 million.

But developing island nations rarely have the resources to implement sophisticated sea defences such as the dykes which keep the water at bay in low-lying areas of the Netherlands.

"The very survival of island nations is at stake," according to French climate expert Michel Petit.

"Even if we completely stabilise concentrations of greenhouse gases in the atmosphere, ocean levels would still continue to rise for centuries," he said. Greenhouse gases are those which raise heat and damage the ozone layer, allowing in harmful solar and other radiation.

Jean Jouzel, the French representative on the UN climate panel, warns that the oceans could eventually rise by four or five metres by the 24th or 25th century -- if, as some experts fear, the glaciers of Greenland also melt.

"(Greenland's) coastal regions are already visibly melting," said Jouzel, warning that many islands would be unable to fend off such a dramatic change.

"Although it is possible to build protection against a one-metre rise, I fail to see how we could protect ourselves against four, five metres," he said.

Among the world's most vulnerable to global warming, the South Pacific atoll nation of Tuvalu has long warned it is at risk from a rise in sea levels.

Last February, the nine islands that make up the archipelago were briefly flooded by high, or "king" tides reaching three metres above sea level, whereas the islands' highest point is just 4.5 metres high.

"We don't need more scientific research about the problem of rising sea levels, it is already happening," Tuvalu's Prime Minister Saufatu Sopo'aga had said at the time.

The giant tides, once an extremely rare occurence, now appear to be taking place at regular intervals, twice per year, and could eventually force Tuvalu's 11,500-strong population to relocate to New Zealand.

While the lack of an early-warning system has been blamed for the heavy death toll in last month's tsunamis, there is no guarantee the world will help poor island nations protect themselves from the threat of rising ocean levels.

Current trends show the states being left to fend for themselves, with international development aid to small island nations having fallen by half between 1994 and 2001, according to the United Nations.