Former President Clinton warned Australians that global warming could cause some small Pacific nations to disappear beneath the ocean, creating a refugee crisis far worse than the one Australia has faced in the last two weeks.

At a hospital fund-raising dinner in Sydney on Saturday, Clinton said hundreds of thousands of people around the world would become refugees if climate change isn't addressed.

"The science is unassailable. If the world keeps growing for the next 50 years warmer as it has for the last decade, you're going to see some of the small nations in the Pacific actually flooded," he said.

"If you're worried about 400 people, you just let the world keep warming up like this for the next 50 years and your grandchildren will be worried about 400,000 people," he added.

Early last week, the Australian government sparked international criticism by barring a Norwegian ship carrying 433 asylum seekers from docking in Australia.

Prime Minister John Howard said he wants to stem a tide of would-be immigrants who arrive each year by the thousands hoping to be given refugee status.

Climate change has been a topic of contention between the United States and other countries. Earlier this year, the Bush administration abandoned the Kyoto climate treaty aimed at stopping global warming, saying it would harm the U.S. economy.

Bush has said he would instead rely on voluntary actions by industry and development of new technologies to capture carbon releases and reduce energy use.

Earlier Saturday, Australia's navy intercepted another boat carrying about 200 suspected illegal immigrants to Australia.

The asylum seekers were being taken to Papua New Guinea before flying to New Zealand and the Pacific island of Nauru for processing of their asylum applications.

Clinton's speech at the fund-raising dinner for Sydney's Westmead Children's Hospital is his only public appearance during a three-day visit to Australia.