NAIROBI, Kenya - The new U.S. administration wants a legally binding international treaty to reduce mercury in the environment, a senior diplomat said Monday, announcing a reversal of previous policy.

Mercury finds its way into the food supply and is commonly found in high concentrations in fish. Children and fetuses are particularly vulnerable to effects of the toxic metal, which can damage the development of the nervous system.

The U.S wants negotiations to begin this year and conclude within three years, said Daniel Reifsnyder, the deputy assistant secretary of state for environment and sustainable development.

"We're prepared to help lead in developing a globally legally binding instrument for mercury," Reifsnyder told an annual meeting of the world's environment ministers in the Kenyan capital.

A U.S.-drafted proposal obtained by The Associated Press would, if passed by the environment ministers, see a negotiating committee formed and the U.N. environment program helping countries reduce their mercury use, among other things.

"It is clear mercury is the most important global chemical issue facing us today that calls for immediate action," Reifsnyder said, referring to mercury's ability to stay in the environment for a long time and be carried across the world.

Advocacy groups that have been working on getting such a global pact passed welcomed the U.S. policy change, saying it could encourage other countries such as Canada to make a similar change.

"Given that the United States has pushed the door of resistance in a sense, that will lead others to follow," said Susan Egan Keane of the Washington, D.C.-based Natural Resources Defense Council.

Mercury is widely used in chemical production and small-scale mining. The extremely dense, toxic metal persists in the environment once released and can travel across the globe. Mercury collects in some species of fish, prompting health warnings in many countries.

While substitutes exist for almost all industrial processes that require mercury, more than 50 per cent of mercury emissions come from coal-fuelled power plants, making its regulation politically charged and extremely difficult.

The policy of the administration of former U.S. president George W. Bush was supported by industry. It allowed utilities to purchase emission credits instead of actually reducing emissions.

The European Union has banned mercury exports from the region starting in 2011. The U.S. has a similar ban that will be effective in 2013. The U.S. legislation that effected the ban was sponsored by President Barack Obama when he was a U.S. senator.