WASHINGTON - An American politician is trying to have the manufacture stopped of a poison used on possums - because it could be used by terrorists to pollute America's water supplies.

New Zealand is the world's heaviest user of Compound 1080 poison - its main weapon in the fight against possums stripping the nation's native forests and spreading diseases - and takes about 80 per cent of the total production from a small factory in Oxford, Alabama.

However, the poison is next year expected to be given its first regulatory review in New Zealand since its initial registration in 1964, as the Environmental Risk Management Authority decided there were grounds for reassessment.

But Oregon's Democrat member of the House of Representatives, Peter DeFazio, wants Alabama's Tull Chemical Co to shut down altogether its manufacture of Compound 1080, also known as sodium fluoroacetate.

Mr DeFazio has asked the Department of Homeland Security to ban production of the odourless, tasteless poison because he says the Federal Bureau of Investigation (FBI) and other agencies believe that 1080 - the most toxic pesticide registered by the World Health Organisation - could be used by terrorists.

Less than 1ml can kill an adult and there is no known antidote.

But Mr DeFazio - a member of the US select committee on homeland security - has argued that the opportunity for misuse of the chemical is not justified by its use in the USA to kill 20 or 30 coyotes.

The Associated Press newsagency reports that Tull Chemical owner Charles Wigley defended his product as safe when used properly, and that other chemicals could be just as deadly in the hands of terrorists.

Mr Wigley said he followed US law and laced his poison with black dye that would show up if it was used by terrorists in a public water reservoir.

Mr Wigley said he made as much as five tonnes of the poison annually, most of it being exported to New Zealand for use against possums.

The poison is also used in Australia to kill foxes, dingoes, wild pigs and rabbits.