"For environmental issues, if you wait until the crisis happens, it will be too late," Omi told reporters in the Malaysian capital.

"Everybody is interested in economic development, but somehow we have to strike the balance between this development and the preservation of nature," Omi added. "And unless we do the action now, we will be faced with very serious consequences."

The WHO had been successful in urging member states to prepare themselves to fight communicable diseases, such as SARS and bird flu, Omi said, but similar action was needed in preparing for likely environmental disasters.

"That kind of preparedness should also be applied to environmental issues, because we know it is just a matter of time," he added. "Unless we take action for the environment, disaster will come."

Rising global temperatures are melting Himalayan glaciers, threatening to inundate low-lying atolls and create unsanitary conditions that breed disease, destroy crops and compromise food supplies, Omi told a WHO workshop on climate change.

"Increasing temperatures are among the variables that affect malaria, and the disease is emerging and re-emerging in places where it did not exist before, or for a long time," he said.

The mosquito-borne disease had been found in the highlands of Papua New Guinea this year, he added, after re-emerging in South Korea in late 1990.

Rising temperatures had also driven a surge in dengue fever in Asia, Omi said.

In the tiny city state of Singapore, for example, the mean annual temperature rose to 28.4 degrees Celsius in 1998 from 26.9 Celsius in 1978, contributing to a more than 10-fold increase in dengue cases over the two decades.

Fighting global warming and rising emissions would require innovative tax incentives and subsidies for clean energy or energy-saving industries, besides the development of environmentally friendly technologies, and lifestyle changes to cut the use of cars.

By gathering evidence of the negative impact of climate change, the WHO hoped to get countries to change their ways, Omi added.