DES MOINES, Iowa – Genetically modified sugar beets designed to withstand the weedkiller Roundup can be planted under strict conditions with no threat to the environment and other plants, the U.S. Department of Agriculture said Friday in a decision anxiously awaited by farmers.

The agency's Animal and Plant Health Inspection Service said it would partially deregulate so-called Roundup Ready beets, letting farmers plant them while it finished work on a full environmental impact statement.

Last summer, a federal judge in California issued an order last summer halting the planting of genetically modified sugar beets until the USDA completed an environmental impact study on how the beets could affect conventional crops. The ruling had a widespread impact since nearly all the nation's sugar beets come from the genetically altered seed, and farmers had worried the USDA wouldn't finish its work in time for spring planting.

"This is a really big deal," said Mike Moyle, a Republican lawmaker who used to grow sugar beets and still farms west of Boise, Idaho. "If they hadn't approved this, farmers in Idaho wouldn't have had enough (unmodified) seed."

Sugar beets are planted on more than 1 million acres in 10 states, with Idaho, Minnesota and North Dakota being the top producers. The beets supply half the nation's sugar, and about 95 percent are grown with the Roundup Ready seed developed by St. Louis-based Monsanto Co.

"USDA's decision is a positive step for sugar beet farmers," said Steve Walker, a Monsanto sugar beet representative. "Sugar beet farmers have been busy for spring planting, waiting for USDA's guidance and hoping it would come in time for spring planting."

Walker said Monsanto will carefully review the details of the interim measures.

The USDA website lists 18 requirements for farmers planting genetically modified sugar beets. They include restrictions on planting in California and several counties in Washington; maintaining a 4-mile distance between the male plants and all other commercial crops; properly cleaning cultivation and harvesting equipment to prevent modified seeds from being mixed with unmodified ones; and a labeling system to identify genetically modified seeds throughout the production process.