On Sunday, President Bush called on Congress to consider a larger role for U.S. armed forces in responding to natural disasters, as he completed what White House aides called a weekend "fact-finding" mission to determine whether the Pentagon needs more control.

"Clearly, in the case of a terrorist attack, that would be the case, but is there a natural disaster -- of a certain size -- that would then enable the Defense Department to become the lead agency in coordinating and leading the response effort?" Bush said after a briefing from military leaders at Randolph Air Force Base here. "That's going to be a very important consideration for Congress to think about."

Bush has told aides that one of the major breakdowns in the Hurricane Katrina response was the federal government's inability to seize control of rescue and relief efforts. Under existing law and procedure, a state governor is in charge when natural disasters strike and is responsible for deploying the National Guard, though in certain cases, the president can order troops to support local law enforcement.

Bush is asking Congress to consider a major change, potentially shifting federal responsibility for major natural disasters from the Department of Homeland Security to the nation's top military generals. The Defense Department has been hesitant to take such a role because of sensitivity to the idea of adopting a police presence on U.S. soil and because of strains on the armed forces from the war in Iraq.

Russ Knocke, a spokesman for the Department of Homeland Security, said a number of ideas are circulating. But Knocke described a narrower role for the military than becoming "the lead agency" for large natural disasters, now the purview of the Department of Homeland Security.

"We are not talking about DOD taking over federal response efforts to a catastrophe from start to finish," Knocke said. Instead, he cited three examples -- maintaining social stability, urban search-and-rescue support, and damage assessment -- when state, local or other federal agencies are incapacitated or overwhelmed.

"We're talking about an ultra-catastrophe, where the need is such that the military's training and assets would meet an immediate need in support of Homeland Security coordination of the federal government's responsibility and recovery efforts," Knocke said.

Some skeptics have said Bush's remarks belatedly recognize that his administration and Louisiana Gov. Kathleen Babineaux Blanco (D) bungled in applying the military's existing capabilities to rescue Katrina victims. Rather than creating new laws and authorities, government officials simply need to execute existing plans competently, they said.

Federal law, response plans and congressional studies -- plus what happened this past week for Hurricane Rita -- make it plain that there is already abundant authority to request the military. But critics said that Bush and Blanco were too slow to do so for Katrina.

Under the new National Response Plan unveiled last winter, local military commanders are authorized and pre-approved "to respond to requests of civil authorities" for "immediate response" needs, including rescue, evacuation, medical treatment, restoration of vital services and safeguarding and distribution of food and supplies, said Michael Greenberger, director of the Center for Health and Homeland Security at the University of Maryland School of Law.

The military is also allowed to provide whatever other disaster support is necessary. Traditionally the military acts at the behest of the lead federal agency -- in the case of a natural disaster, it would be the Federal Emergency Management Agency and DHS -- and waits until requested to provide large numbers of troops. There are exceptions when the military has acted on its own, as a commander did in response to the 1906 San Francisco earthquake.

The current National Response Plan developed after the Sept. 11, 2001, terrorist attacks gives the defense secretary authority to provide military support for disaster relief efforts at the president's direction.

However, active-duty troops generally cannot take on domestic law enforcement roles, which is what many experts said was desperately needed to stop the rioting and violence in the streets of New Orleans after Katrina hit. National Guard troops under state control are allowed to take on law enforcement responsibilities.

At Randolph Air Force Base, Maj. Gen. John White urged the president to create a national plan to better coordinate search-and-rescue efforts after major disasters. White said one glaring example of planning errors was when five helicopters showed up at the same time to rescue one person in New Orleans.

"That's the sort of simplistic thing we'd like to avoid," White said to Bush. "That was a train wreck that we saw in New Orleans."

"Part of the reason I've come down here, and part of the reason I went to Northcom, was to better understand how the federal government can plan and surge equipment, to mitigate natural disasters," Bush said. "It's precisely the kind of information that I'll take back to Washington to help all of us understand how we can do a better job in coordinating federal, state and local response."

Bush met this weekend with officials in Colorado Springs at the headquarters of the U.S. Northern Command, before traveling to Austin, San Antonio and Baton Rouge, La.

Defense officials in Washington have been closely examining the Katrina response to see how the military can better react to similar disasters, especially in terms of supporting local "first responders" such as police, fire paramedic and hazardous-materials officials in the event a crisis renders them ineffective.

Paul McHale, assistant secretary of defense for homeland defense, said last week that the department will be looking at "more realistic training exercises so that we can more effectively address a catastrophic event that similarly degrades or destroys the local first responder community," and that there needs to be an emphasis on communications and damage assessment. He also said the active-duty military and the National Guard need to work together more closely.

White reported from Washington. Staff writer Spencer S. Hsu in Washington contributed to this report.

President Bush visits a FEMA office with Louisiana Gov. Kathleen Blanco.