Such a precedent-setting shift would require not only some change in law but a greater degree of consensus. Congress is divided over the prospect of troops massed in U.S. cities and increasing the power of the federal government at the expense of the states.

And there's the question of what would be left for the recently created Homeland Security Department to do.

Bush has described the armed forces as ''the institution of our government most capable of massive logistical operations on a moment's notice,'' and defense analysts echo that assessment.

With its wealth of all-terrain vehicles, helicopters, boats, satellites and coordination and control operations, the military can quickly dispatch what a lot of people need in a hurry after a disaster, whether that means 1,000 choppers to pluck residents from rooftops or shallow-water vessels to navigate flooded streets.

Still, the Pentagon seems lukewarm about taking control and providing the core of disaster relief. ''It's something we've thought about,'' Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, said Tuesday. But he said there is a long way to go before ''you ... decide you want to give active forces law enforcement authority.''

Retired Gen. Charles E. Wilhelm, who accompanied the Army general in charge of the military's hurricane response, said civilian agencies, not the Pentagon, should continue to lead the response.

Turning the military into first responders risks making it ''a jack-of-all-trades, master of none.''

In response to Rita, Navy and Air Force teams, flying from the deck of the USS Iwo Jima and Randolph Air Force Base in Texas, conducted rescue missions into Texas and Louisiana. During the weekend, they transported several thousand people to safety, including 1,300 patients.

Four Navy ships were off the Gulf Coast on Tuesday, providing hurricane relief, including the salvage ship USS Grapple, which was beginning survey operations. About 600 members of the 82nd Airborne Division were sent from New Orleans to southwestern Louisiana late Monday to assist in rescue and recovery.

''The military has more plans on the shelves that you can kick a stick at, and that's a good thing,'' said retired Adm. James M. Loy, a senior counselor at the Cohen Group who was commandant of the Coast Guard and deputy in the Homeland Security Department for two years.

The U.S. Northern Command, which began operations in October 2002 as the first command with the United States in its area of responsibility, assists the Federal Emergency Management Agency in disaster relief and has the organizational skills.

''In some disaster unforeseen, you need somebody right away, and the active duty military is of course, organized and together on one installation where you can move them quickly,'' said Robert Gard, a senior military fellow at the Center for Arms Control and Non-Proliferation.

This unique ability comes at a price -- more than $400 billion a year.

''Do we want to have that mobilization capability in non-defense agencies?'' asked Clark Murdoch, a senior adviser at the Center for Strategic and International Studies. With Katrina, ''We had the 82nd Airborne on alert for 24 hours and no one pulled the trigger on them for three or four days.''

The all-volunteer force also is stretched thin by fighting in Iraq and Afghanistan and an added role would require an influx of troops. The armed forces' unique chain of command would prove difficult to impose on elected civilian officials.

''It's a terrible idea to put the military in charge because they still have a day job,'' said James Jay Carafano, a senior fellow at the Heritage Foundation who taught at West Point and co-authored a book on homeland security. ''What happens if the Iraq invasion had coincided with Hurricane Katrina? Does (Secretary of Defense Donald) Rumsfeld stop the war to do Hurricane Katrina?''

The military's purpose, its training and exercises are not geared to domestic operations or law enforcement.

''The military as an institution is not too fond of this thing,'' said retired Air Force Gen. Charles G. Boyd, president and CEO of Business Executives for National Security. ''They're the lethal arm of American foreign policy. They fight the nation's enemies.''

The military is prohibited from performing law enforcement duties by the Posse Comitatus Act of 1878, enacted after the Civil War. But the Insurrection Act does allow the president to call troops into federal action inside the United States when there is a threat to authority.

President Eisenhower sent troops from the 101st Airborne to Little Rock, Ark., and also federalized the Arkansas National Guard in 1957 to ensure the integration of Central High School. President Kennedy ordered federal troops to Oxford, Miss., to stop the riots precipitated by James Meredith's enrollment at the University of Mississippi in 1962.

Making the military the lead agency and sending troops after a hurricane could upset local officials.

''The federal government does not lightly put troops into states, particularly Southern states, without the request of the governor,'' Richard A. Falkenwrath, a former deputy homeland security adviser, told a recent conference. ''It's a very big deal, if the government were to do that unilaterally.''

Sen. John Warner, R-Va., chairman of the Senate Armed Services Committee, said his panel would review a specific proposal from the president.

Associated Press writers Larry Neumeister in Hattiesburg, Miss., and Lolita C. Baldor in Washington contributed to this report.