Traces of the 12 so-called persistent organic pollutants (POPs), swept around the globe by air or ocean currents, have been found even in the breast milk of Inuit women in the Arctic and have been blamed for turning polar bears into hermaphrodites.

Meeting in Stockholm, about 50 environment ministers and senior officials from more than other 70 nations will on Tuesday formally agree a deal to ban or restrict use of the chemicals, a pact which was hammered out in December in Johannesburg.

They will hold preparatory talks on Monday and sign the agreement on Wednesday. Under the pact, use of the POPs will be banned or heavily restricted.

The United States, under fire even from its allies since President George W. Bush pulled out of a global agreement aimed at combating global warming, will be among those signing - in a sign that it is not abandoning all environmental cooperation.

But the so-called Stockholm Convention is less controversial - many of the 12 chemicals have been known killers for decades and have been banned in many industrial nations. And costs of eliminating them are far lower than fighting climate change.

"Every single nation is going to have to do something it is not already doing to comply," Jim Willis, director of chemicals for the United Nations Environment Programme (UNEP), told Reuters.

RICH COUNTRIES STILL EXPORTING

Among the chemicals covered by the pact are the pesticides and insecticides aldrin, chlordane, dieldrin and endrin, blamed for inadvertently killing fish and birds. Dioxins and furans, the unwanted by-products of chemical production or burning, have been linked to serious illness in humans.

Also on the list are polychlorinated biphenyls, used as heat exchange fluids or as additives in paint and plastics and believed to have caused disorders in animals and birth defects in humans. The anti-malarial DDT, already widely restricted, is included as are several chemicals believed carcinogenic.

Some rich nations are still producing POPs for export even though they are banned at home.

"It'll be a victory for the environment if the words on paper and from the ministers are turned into concrete actions," said Darryl Luscombe of Greenpeace.

"It's obviously good that the United States has agreed to sign and ratify. But of course they should also take their other international commitments just as seriously," he said. Bush earlier this year rejected the 1997 Kyoto pact aimed at curbing emissions of greenhouse gases.

Luscombe said more chemicals than the dozen listed should be included in pact, among them brominated flame retardants used in many modern computers.

Developing countries will be able to draw on a proposed fund of $2.5-$3.5 billion to help clean up, Willis said. The U.N. Food and Agriculture Organisation said last week that 500,000 tonnes of ageing pesticide waste threatened millions of people in developing nations.

And the deal includes some opt-outs.

Nations including South Africa successfully argued that they needed to keep using the pesticide DDT to fight malaria.

DDT, sprayed on walls, keeps away mosquitoes even though DDT itself has been tied to chronic health problems in humans. Malaria is worse, killing more than a million people a year.