The United States, the European Union and Japan have cut the use of methyl bromide to 30 percent of previous levels, but now the United States wants to be allowed to increase its use to 38.2 percent in 2005.

Conference spokesman Nick Nuttall said an extraordinary meeting of parties to the Montreal Protocol would take place in Montreal in March next year."

"It would be designed to resolve the difficulties we had at this meeting. We are disappointed that there was no consensus," U.S. delegation head Claudia McMurray told Reuters.

Methyl bromide, which kills soil pests before crops are planted, is due to be phased out by all developed nations by January 1, 2005, under a global pact to protect the atmosphere.

A U.S. government delegation and farm groups say although they have made significant cutbacks in its use, they need more time to find effective substitute fumigants for crops such as tomatoes, peppers, eggplant, strawberries and sweet potatoes.

Around 180 signatory countries to the Montreal Protocol had been due to vote on the U.S. request Friday at the close of a meeting on the ozone layer at the U.N. Environmental Program headquarters in Nairobi. That vote did not take place.

The protocol - seen by experts as the most successful of various global environmental treaties - requires signatory states to phase out the use of some 95 chemicals that damage the ozone layer, a stratum of the atmosphere that protects the Earth from ultraviolet radiation.

METHYL BROMIDE ALTERNATIVE

Dow AgroSciences, a subsidiary of the largest U.S. chemical maker, The Dow Chemical Company, said its a soil fumigant, telone, was used widely in tomato and strawberry farms and unlike methyl bromide does not damage the ozone layer.

"We're not here to say the U.S. government is wrong but we're here to reinforce that there are alternatives to methyl bromide," the company's global business leader Jeffrey Welker said, adding that telone is used in 30 countries, including the United States.

Ozone experts and EU delegates opposed the U.S. request because it could reverse the gains achieved so far.

"It is the first time we are going to have an extraordinary meeting. We came here to negotiate but some parties came with a higher position and were not prepared to negotiate seriously on this," said Peter Horrocks, the head of the EU negotiating team.

David Doniger, policy director at the U.S.-based advocacy group Natural Resources Defense Council calls methyl bromide the most dangerous ozone-depleting chemical still in widespread use and also a cause of prostate cancer.

Mark Murai, chairman of the 600-member California Strawberry Commission said: "We wanted a decision as soon as possible but we also wanted a favorable outcome. Farmers will be in limbo on what to do because they needed to know in advance so that they can plan for their crops."