GENEVA, NOV. 6 -- Jordan's King Hussein, taking his plea for peace to a United Nations conference on global warming, declared today that if war broke out in the Persian Gulf the world would suffer an ecological catastrophe and death toll "beyond our wildest fears."

On the topic of the conference, British Prime Minister Margaret Thatcher -- citing her credentials as a chemist turned politician -- said, "The danger of global warming is as yet unseen, but real enough for us to make changes and sacrifices, so that we do not live at the expense of future generations."

Hussein urged government representatives from more than 120 nations to undertake "all possible efforts to resolve the gulf crisis through peaceful negotiations" because the confrontation building between Iraq and U.S.-led multinational forces "is taking place literally on top of the single richest natural petroleum reservoir in the world, which accounts for over half the world's mineral energy resources."

He said a war in the gulf "would not only result in devastating human deaths and injury, tremendous economic loss and prolonged political confrontation," but would also lead to a disaster for the global environment "the likes of which the world has not experienced since the accidents at the Chernobyl nuclear power plants, which sent shock waves around the world."

Iraqi President Saddam Hussein has threatened to destroy the region's oil fields if war breaks out and Iraq is believed to have wired explosives to refineries and wellheads in Kuwait.

Oilfield engineers and experts in oil-well fires say there is no possibility that underground reserves could burn because of the lack of oxygen, but that extremely hot, smoky fires that would darken the skies for several days over a radius of hundreds of miles are possible. Storage tanks at Kuwait's refineries and export terminals are believed to hold many millions of barrels of crude oil, gasoline and jet fuel.

Fires at these installations, whether set by retreating Iraqis or ignited by bombs and artillery shells, could melt metal and send toxic gases into the atmosphere, experts say.

King Hussein's depiction of oil fields set aflame by modern weaponry, blackening skies for hundreds of miles around the gulf, came as Thatcher and other leaders here called for urgent action to slow the release of "greenhouse gases" that scientists predict will raise world temperatures alarmingly if nothing is done.

Thatcher said that global warming, besides raising sea levels -- which scientists say could flood coastal regions and displace millions of residents -- would affect other problems of this age, including the population explosion, soil deterioration, growing pollution of the seas and the destruction of forests.

Thatcher said that while more research was necessary, this "should not be an excuse for delaying" commitments by all nations to curtail emissions of carbon dioxide that get trapped in the atmosphere. Her words were echoed by French Minister Michel Rocard, who warned the delegates that they face "a race against time . . . to save our planet."

Eighteen European countries agreed last week to stabilize their carbon dioxide emissions at current levels by the start of the next century. But efforts by the European countries to fix global targets have been opposed by the United States and the Soviet Union, which between them produce more than 50 percent of the greenhouse gases because of their huge consumption of fossil fuels.

The United States, which sent a delegation headed by the director of the National Oceanic and Atmospheric Administration, has opposed setting targets for standards in the final declaration, due to be released after the concluding session Wednesday. Despite some policy conflicts within the Bush administration, the U.S. position at the conference prescribes more research to clarify the true impact of greenhouse gases on the environment and the avoidance of any measures that might constrain economic growth.

Developing countries also have viewed the debate with suspicion because they fear being asked to share in the cost of cleansing a global environment polluted largely by industrial nations. They contend that their growth prospects should not be unfairly shackled by restrictive environmental concerns.

Staff writer Thomas Lippman, in Washington, contributed to this story.