The Southern Shrimp alliance said in a statement that imports "from countries such as Thailand, China, and Vietnam" are "causing market distortions that harm the US shrimp industry."

Details will be made public after the case is filed Wednesday, said Brad Ward with Dewey Ballantine LLP, the Washington law firm handling the case.

Alliance spokeswoman Deborah Regan said that countries in southeast Asia and Latin America had been targeted, but refused to give further details.

The Alliance represents shrimp harvesters, processors, and distributors from eight US states.

In mid-December representatives of Mexico's National Chamber of Fishing and Aquaculture Industries met with the Alliance and agreed to cooperate "to jointly oppose unfair trade in shrimp.

"The flood of unfairly traded shrimp injures both the US and Mexican shrimp industries and must be offset through strong enforcement of the trade laws in our two countries," representatives said in a joint statement at the end of their meeting.

According to US government figures, in 2002, shrimp passed tuna to become the number one consumed seafood in the United States. Americans consumed 3.4 pounds (four kilos) of shrimp per person in 2001, up 9 per cent from 2000.

However while in 2000 the value of the US shrimp harvest was 1.25 billion dollars, by 2002 that had plunged to a mere 559 million due to competition from cheap imports.

The president of the year-old Shrimp Alliance, Eddie Gordon, said earlier that shrimping in the United States "has always been more than just a business, it has been a way of life.

"Today, our tradition, our way of life is threatened. Shrimpers, their families, related businesses, and many communities dependent on shrimping are experiencing serious economic harm. We are nationally united for the first time to prevent this."