The EU is calling for deadlines, bans and detailed promises, whereas the U.S. prefers partnerships between industries and governments with no specific goals or deadlines for reducing either the global supply or demand of mercury.

In 2001, the United Nations Environment Program, or UNEP, declared that "national, regional and global actions, both immediate and long-term, should be initiated as soon as possible" to reduce emissions of mercury, a potent neurotoxin that has contaminated fish and other food sources around the world.

Meeting at UNEP's world headquarters in the Kenyan capital through Friday, more than 100 environmental ministers from six continents will decide whether to begin drafting a binding international treaty to restrict the buying, selling and use of mercury.

Whether for small gold mines in Ghana or chemical factories in Louisiana, mercury is traded freely as a commodity on the world market. Every year, about 3,400 tons are purchased for use in industrial processes, particularly chlorine manufacture, and in products such as batteries.

Mercury is a natural element in the Earth's crust. When industries release it into the air, however, it travels great distances, contaminating oceans, lakes and rivers. The amount of mercury found in one out of six Americans exceeds levels that could cause neurological and developmental damage in a fetus or infant, according to the U.S. Environmental Protection Agency.

Unlike most other pollutants, mercury is used primarily in the developing world, not industrialized countries.

Coal-burning power plants are the largest source of mercury emissions in the U.S. - and in the world. But restrictions on the power industry will be left to individual nations under all the plans under consideration. Mercury alloys used in dental fillings also would remain unaffected. The four industries that buy and sell mercury are the focus of the U.N. debate: chlorine production; battery manufacturing, which occurs mostly in China; small-scale gold mining in Africa, Brazil and Southeast Asia; and mercury mines in Spain, Kyrgyzstan, Algeria and China.

"Mercury mismanaged anywhere in the world contaminates U.S. food supplies," said Linda Greer, director of environmental health for the nonprofit Natural Resources Defense Council. "Mercury escaping from outdated chemical factories in India may easily appear in fish at a Manhattan grocery store or caught by anglers here in the U.S. Great Lakes."

In a report last year, the European Commission, the EU's executive body, concluded that mercury should be considered a special case for trade restrictions because "it does not make economic or environmental sense for the European Commission to protect the free-functioning market for a toxic substance."

In its proposal to the U.N., the EU vowed to end all exports by 2011, shut down its only mercury mine and close old chloralkali plants that use vats of mercury to produce chlorine. It wants the rest of the world to commit itself to doing the same.

But the Bush administration opposes a binding treaty. Instead, it has called for creating partnerships between industries, governments and environmental groups to share information about mercury-free technologies, health advisories on contaminated fish and the best business practices.

Claudia A. McMurray, deputy assistant secretary for the environment at the State Department, said partnerships are the best option because negotiating a treaty could drag out five to eight years. Many developing nations, she said, do not even understand the extent of their emissions yet or the possible solutions, so they are unprepared to negotiate and cannot commit themselves to milestones.

"A one-size-fits-all set of deadlines is not necessarily the right answer," McMurray said. "We see more individualized solutions."

At least 10 nations have shown interest in the partnerships, and the U.S. this week plans to pledge more than $1 million next year to support the U.N.'s mercury program.

The partnerships, McMurray said, would "make all the countries involved accountable. While they don't have a UNEP deadline attached to them, we would make a public commitment and the public could hold us to it."

Environmental groups in the U.S. and Europe accuse the administration of impeding any meaningful global progress and protecting U.S. industry. "It's even worse than a weak starting point," Greer said.

"It's a cover-up for not doing anything about the mercury problem. A partnership needs milestones and goals and timelines. Otherwise it will just be a meeting in Geneva twice a year."

Facing a divisive debate, the secretariat of UNEP has pieced together a directive that merges the U.S. partnerships proposal with one from Switzerland that would start crafting a binding treaty. Europe has proposed amendments that would close all mercury-using chlorine plants by 2020, restrict mercury batteries by 2010 and implement a strategy to reduce the metal's use in gold mines by 2007.

UNEP officials say developing nations are likely to side with the Bush administration out of fear that mercury supplies will be cut off. But they are eager to see whether the developed world - especially Japan, Canada and Australia - aligns with the U.S. or with Europe.

UNEP's governing council hopes to vote Thursday or Friday.

"What seems certain is that there is support for further activities on mercury. The discussions are on what form they should take," said Aase Tuxen, scientific affairs officer of UNEP's chemical division. Europe and Asia have the most at stake economically.

Europe is the world's largest exporter of mercury, while China and India are the biggest users.

In the U.S., the only industry with a sizable economic stake is the chlorine industry, which purchases about 130 tons of mercury per year. Most chlorine manufacturers worldwide have already switched to mercury-free technology. But more than 135 chloralkali plants still use vats of mercury to trigger a chemical reaction, including nine in the U.S.

EPA spokeswoman Cynthia Bergman said the U.S. already had reduced its mercury emissions by more than 45% since 1990. Next month, the EPA will impose a new rule that caps mercury released from power plants.