The preliminary ruling in Geneva on Tuesday was hailed by US officials and industry leaders, who have argued a de facto EU moratorium on genetically modified organisms (GMOs) lacks a scientific basis.

"This decision affects not only Argentina, Canada and the United States, who prevailed in this complaint, but the future of agricultural biotechnology for all countries," said CS Prakash, president of the AgBioWorld Foundation in Auburn, Alabama, which promotes biotechnology.

"This ruling enables developing nations to feel confident that they can adopt the modern crop technologies they need to feed their people while retaining access to European export markets."

Prakash said some 90 million hectares (222 million acres) were planted with biotech crops last year, one-third of which was in developing countries.

US Trade Representative Rob Portman said that if the ruling stands, it would be an important step for biotech crops around the world. The decision affected mainly corn, soybeans and cotton crops.

"It is a safe and beneficial technology that is improving food security and helping to reduce poverty worldwide," he said.

"We believe agricultural biotechnology products should be provided a timely, transparent and scientific review by the European Union, and that is why Canada, Argentina and the United States brought the case in the first place."

Chris Horner, spokesman for Monsanto, one the leading US companies in biotech, said the impact on the company's operations was not yet clear.

"Our feeling is that it's important for (other countries than the EU) to have science-based regulatory frameworks," he said.

Leon Corzine, chairman of the National Corn Growers Association, said his group was pleased with the WTO decision

"It's going to be helpful in world trade," he said, noting that US corn producers export about 17 percent of their harvest.

Corzine noted that Europe represented about one percent of US corn exports in 2004, with 54 percent going to Asia and 11 percent to Africa,