SAN FRANCISCO — A federal appeals court ruled yesterday that Canadian cattle can again be imported to the United States, dismissing a lower-court decision that resuming the imports could spread mad-cow disease.

The U.S. Department of Agriculture said it will reopen the border within days to Canadian cattle, which were banned in May 2003 after a cow in Alberta was found to have mad-cow disease. Agriculture Secretary Mike Johanns said the government was working with Canadian food inspectors to certify cattle for shipment.

The unanimous decision by a three-judge panel of the 9th U.S. Circuit Court of Appeals overturns a Montana judge who blocked the USDA from reopening the border in March, saying it "subjects the entire U.S. beef industry to potentially catastrophic damages" and "presents a genuine risk of death for U.S. consumers." The justices said they would issue another ruling explaining their rationale.

The decision came a day after the Justice Department urged the appeals court in Seattle to reopen the border to imports. Justice Department attorney Mark Stern said lifting the ban is based on "good science" and would not result in the "infestation in American livestock."

During the hearing, the three judges suggested that U.S. District Judge Richard Cebull perhaps should have given deference to the USDA's decision.

Judge A. Wallace Tashima said the law "does invest the secretary of agriculture with a certain amount of discretion."

Judge Connie Callahan agreed, saying the USDA is "entitled to some deference. It's their whole job to keep up with the science to make those decisions."

American Meat Institute President J. Patrick Boyle said the industry will be able to resume cattle shipments quickly. "A lot of the preliminary work is already done. I think you'll see the industry move quickly," he said.

Boyle said the ruling is also "a win for American consumers who were paying $1.85 a pound for ground beef before the border closed and are paying about $2.55 today."

But Bill Bullard, director of the Ranchers Cattlemen Action Legal Fund, said the USDA "did not provide significant justification for overturning a long-standing policy that protected both the U.S. cattle herd and U.S. consumers" from mad-cow disease.

Mad-cow disease is the common name for bovine spongiform encephalopathy, or BSE. People who eat tainted meat can contract a degenerative, fatal brain disorder called variant Creutzfeldt-Jakob disease. More than 150 people died from it after a 1986 outbreak in the United Kingdom.