Many environmental and consumer groups, especially in Europe, have opposed GMOs, saying more research was needed to ensure they are safe for humans and the environment.

The U.S. Agriculture Department said in its annual acreage report that 75 percent of the soybeans planted by U.S. farmers this year contained genetically modified organisms (GMO), up from 68 percent in 2001, and 1 percentage point above its March pre-planting estimate of 74 percent.

USDA said 34 percent of the corn planted had GMOs, up from 26 percent last year and 2 points above its March estimate.

GMO cotton accounted for 71 percent of total plantings, up 2 points from last year and unchanged from the March estimate.

The United States is the world's largest producer of crops that are genetically modified to make them resistant to pests or to withstand herbicides that kill nearby weeds.

In September 2000, the detection of StarLink corn sparked a nationwide recall of products such as taco shells from grocery shelves because the variety had not been approved for human consumption because of fears it might cause allergic reactions.

U.S. corn exports to top markets such as Japan and South Korea slumped, causing some farmers who claimed to have suffered a loss in income to file class-action lawsuits against the maker of StarLink corn, Aventis CropScience.

"The technology is offering significant values.... Any perceived associated risks such as StarLink are not a major factor in (farmers') decision making process," Kerry Preete, Monsanto's vice president for U.S. markets, told Reuters.

He said Monsanto's share of the biotech corn market was expected to grow by 1 to 2 percentage points this year from last year's total of about 10 percent to 10.5 percent.

Virtually all the GM soybeans grown are Roundup Ready varieties produced by Monsanto to resist the company's Roundup herbicide.

Preete said Monsanto was hoping for approval next year of its new genetically modified Bt corn that is engineered to resist the destructive larvae of a certain corn rootworm pest.

The corn plant, designed to express a naturally occurring pesticide known as Bacillus thuringiensis kumamotoensis, is awaiting USDA approval after four years of field tests.

Greenpeace's Margulis said consumers' opposition to genetically modified foods was reflected in the reluctance of farmers to grow GM wheat, rice, sugar beets and potatoes.

"They have had success in one crop (soybeans) because most Americans don't know they eat soybean products virtually every day," he said. "Consumers know about wheat, lettuce and others."