Citing Pentagon officials, the newspaper said the plan calls for three rapid-reaction forces.

The first 4,700-strong unit, built around an active-duty combat brigade, is based at Fort Stewart, Georgia, and is already available for deployment, according to General Victor Renuart, commander of the US Northern Command, it said.

Two additional groups will later join nearly 80 smaller National Guard and reserve units made up of about 6,000 troops to support local and state authorities nationwide, The Post said.

They will all would be trained to respond to domestic chemical, biological, radiological, nuclear, or high-yield explosive attacks.

The newspaper said that civil liberties groups and libertarians had expressed concern that the plan could undermine the Posse Comitatus Act, a 130-year-old law restricting the military's role in domestic law enforcement.

Before the terrorist attacks of Sept. 11, 2001, dedicating 20,000 troops to domestic response -- a nearly sevenfold increase in five years -- "would have been extraordinary to the point of unbelievable," Paul McHale, assistant defense secretary for homeland defense, said in remarks last month noted by the Post. But the recognition that civilian authorities may be overwhelmed in a catastrophe [Hurricane Katrina might be used as an example] prompted "a fundamental change in military culture."

"The Pentagon's plan calls for three rapid-reaction forces to be ready for emergency response by September 2011," the Post added. "The first 4,700-person unit, built around an active-duty combat brigade based at Fort Stewart, Ga., was available as of Oct. 1, said Gen. Victor E. Renuart Jr., commander of the U.S. Northern Command."

"If funding continues, two additional teams will join nearly 80 smaller National Guard and reserve units made up of about 6,000 troops in supporting local and state officials nationwide," they continued. "All would be trained to respond to a domestic chemical, biological, radiological, nuclear, or high-yield explosive attack, or CBRNE event, as the military calls it."