Paul McHale, assistant secretary of defense for homeland defense, stressed, however, that the expanded active-duty military response would be limited to rare, mass calamities or attacks in which thousands of lives were at risk -- such as a category 4 hurricane, or a terrorist strike involving chemical, biological or nuclear weapons.

Federal troops might also play a role in enforcing a quarantine in the case of a pandemic outbreak of avian flu or other disease, McHale said, although initially that job would fall to National Guard forces under the command of state governors.

"We are looking at a wide range of contingencies potentially involving Title 10 forces [federal troops] if a pandemic outbreak of a biological threat were to occur," said McHale.

In contrast, the Pentagon does not intend to take the lead in responding to the dozens of "major disasters" such as floods declared every year, McHale said. And even in catastrophic events, the Pentagon's goal would be to provide a rapid, early response and then to quickly transfer responsibilities to civilian authorities, he said.

The planning for an expanded Pentagon role in domestic catastrophes comes amid escalating demands on U.S. forces, which today not only are fighting in Iraq and Afghanistan but are also carrying out disaster-relief missions in Pakistan, Guatemala, and domestically along the Gulf Coast.

Defense Secretary Donald H. Rumsfeld, at a conference with Central American defense ministers in Florida, yesterday advocated closer military cooperation as a way to better address threats from terrorists and drug traffickers, as well as natural disasters.

The Pentagon is drafting recommendations for improving the military's response to devastating attacks or disasters as part of a government-wide review of "lessons learned" from Hurricane Katrina.

"It is almost inevitable that the Department of Defense will play a very substantial role in providing resources, equipment, command and control, and other capabilities in response to a catastrophic event," McHale said. Only the Pentagon can "marshal such resources and deploy them as quickly . . . during a time in which thousands of American lives may be at risk."

One major focus will involve identifying a larger active-duty force that will be organized and trained to respond immediately -- along with the National Guard -- to a domestic crisis, McHale said. Advance planning between the active-duty personnel and the Guard is vital -- in contrast to the cooperation that he said unfolded during Katrina "on the fly" -- albeit by "superb leaders."