Temperatures fell, Gulf fisheries collapsed and fresh water supplies were poisoned by fires and giant oil slicks, extending human suffering long after the end of a war in which more than 100,000 people died.

And under Saddam in Iraq, environmentalists widely criticise schemes to drain marshlands at the confluence of the Tigris and Euphrates rivers, displacing hundreds of thousands of Marsh Arabs and causing partial desertification.

The environmental impact of any U.S.-led war to rid Iraq of alleged chemical and biological arms can only be guessed at, but 1991 is a worrying precedent. Saddam says Baghdad will not ignite oil wells and has no weapons of mass destruction.

"The environment of Iraq is already cause for serious concern," said Nick Nuttall, spokesman for the U.N. Environment Programme, which plans a study of Iraq's battered environment whether there is a war or not.

"Over the last few decades there has been damage to the life support system as a result of the Iran-Iraq war, the Gulf War and internal projects such as the drainage of parts of the marshlands," he said.

BANDICOOT RAT EXTINCT

The bandicoot rat and a type of smooth-coated otter, once indigenous to the marshlands, are believed to be extinct. Nuttall said that UNEP wanted to halt and reverse the drainage of the marshes.

"The worst thing about war is that it kills people," said Jonathan Lash, head of the Washington-based World Resources Institute, an independent think-tank. "But there is also huge potential for environmental damage."

"In the Gulf War Iraqi forces ignited 600-700 oil wells, creating a column of smoke that could be seen from space," he told Reuters. "Iraq has about 2,000 oil wells, is more densely populated and has more agriculture than Kuwait."

Even so, he said Gulf fisheries had rebounded more quickly than expected since 1991. About 25,000 birds were killed by oil in 1991 and any new war in coming weeks would disrupt migration routes for birds like pelicans and storks.

Collapse of electricity supplies in parts of Iraq after the Gulf War led to deforestration as people felled trees. And disruption of fresh water supplies helped spread diseases.

The U.N. Children's Fund (UNICEF) said that mortality of children under five more than doubled to 131 per 1,000 live births in the five years to 1999. It said that war and U.N. sanctions on Iraq were partly to blame.

And the U.S. military said that it would hit Iraqi tanks in any new war with depleted uranium ammunition, used in the Gulf War to destroy Iraqi armour and said by critics to cause cancer. U.S. defence officials say the uranium is not a health hazard.