A representative of the U.S. Northern Command says the troops would be trained to help state and local governments deal with a situation that ABC news terrorism consultant Jerry Hauer says "will be unlike any other the country has faced."

However, some security experts are concerned that having an active brigade assigned to duties inside the the country may violate a statute limiting the use of the military for domestic law enforcement.

"By definition, if the troops are operating in a civilian environment they're going to find themselves policing," says Kyle Olson, a homeland security expert.

Ben Friedman, a national security expert with the Cato Institute, told ABC putting troops in the United States would be a "waste" and may "sap their readiness for other missions."

The plan comes on the heels of a new government report the United States is likely to suffer an attack with a biological or nuclear weapon by 2013.

Some 1.1 million active-duty troops are stationed in the United States but not assigned local missions.