PETERSON AIR FORCE BASE, Colo., July 17, 2002— The four-star general in charge of defending the United States against attack said he would favor changes in existing law to give greater domestic powers to the military to protect the country against terrorist strikes.

The Bush administration has directed lawyers in the Departments of Justice and Defense to review the Posse Comitatus Act of 1878 and any other laws that sharply restrict the military's ability to participate in domestic law enforcement. Any changes would be subject to Congressional approval.

The general, Ralph E. Eberhart of the Air Force, said he had no specific changes in mind, but added in an interview here, "We should always be reviewing things like Posse Comitatus and other laws if we think it ties our hands in protecting the American people."

The willingness of General Eberhart and some other senior officers to consider amending the post-Reconstruction law is a shift in thinking by many top Pentagon officials, who have traditionally been wary of involving the military in domestic law enforcement.

Military leaders have generally supported the restrictions because their troops were not specifically trained in those roles, and they worried that domestic tasks could lead to serious political problems.

But in the aftermath of Sept. 11, some Pentagon officials and military officers are beginning to say that the law, as it stands, may slow or complicate their domestic defense missions.

Some military officials fear that without additional authority to operate in the United States, they could be blamed for failures without adequate ability to prevent them. But other Pentagon officials continue to contend that accepting greater domestic responsibilities is risky, and that any proposed changes should receive careful public scrutiny.

All of this reflects the larger national debate over how best to protect Americans from terrorist attacks.

As recently as May, Defense Secretary Donald H. Rumsfeld said the Pentagon would not seek any changes in the law, and the legal review contained in President Bush's new plan for domestic security announced this week surprised many senior officers and Pentagon officials.

But White House officials insisted that administration lawyers review the law to determine whether domestic preparedness and response efforts would benefit from greater involvement of military personnel, reflecting tension between some at the Pentagon and the Office of Homeland Security.

"This was their initiative, not ours," said one senior Defense Department official.

At the same time, however, other senior military officials — including General Eberhart — said the review made sense. The general finds himself in the delicate position of balancing the wariness of his bosses at the Pentagon with his own responsibilities as the leader of the military's new Northern Command, where he will presumably want as much flexibility as possible to carry out his mission.

Other commanders are asking similar questions as the military develops expertise in areas, like information operations and cyberwarfare, that could support domestic law enforcement agencies. Such support is now barred by law, defense officials said.

No one is sure what additional responsibilities the military might take on if the law is revised. White House and Pentagon officials said several incidents since Sept. 11 illustrate why changes may be needed.

When National Guard troops were deployed on the Canadian border after Sept. 11 to support Border Patrol and Customs agents, the Posse Comitatus law prevented those troops from conducting surveillance from the helicopters that flew them to their assignment.

Administration lawyers determined that President Bush would violate Posse Comitatus if he called up National Guard troops to help provide security at airports nationwide. So Mr. Bush had to ask governors to use their call-up authority to perform the same task.

"We think a review is necessary to streamline interpretations of some existing laws," said Gordon Johndroe, a spokesman for the Office of Homeland Security.

The Posse Comitatus Act was enacted after the Civil War in response to the perceived misuse of federal troops who were charged with domestic law enforcement in the South. But it has come to symbolize the separation of civilian affairs from military influence.

Posse Comitatus restricts military forces from performing domestic law enforcement duties, like policing. Over the years, the law has been amended to allow the military to lend equipment to federal, state and local authorities; assist federal agencies in drug interdiction work; protect national parks; and execute quarantine and certain health laws. About 5,000 federal troops supported civilian agencies at the Winter Olympics in Salt Lake City this year.

"My view has been that Posse Comitatus will constantly be under review as we mature this command, as we do our exercises, as we interact with FEMA, F.B.I., and those lead federal agencies out there," said General Eberhart, referring to the Federal Emergency Management Agency.

The Northern Command, which begins operations here on Oct. 1, will be in charge of all military personnel involved in flying patrols over American cities, guarding the waters up to 500 miles off the United States coast, and responding to major terrorist attacks.

In his vision for the new command, General Eberhart said the military could use new technology, like remote-controlled surveillance blimps operating at 70,000 feet and unmanned Predator drones that would patrol American coastlines.

The general said it was also possible that the North American Aerospace Defense Command, known as Norad, might expand beyond the United States and Canada to include Mexico, or that the United States might form a separate joint defense command with Mexico.

"To defend this nation, we have to defend as far out as possible," General Eberhart said. "Therefore we need the support of Canada and Mexico to be able to defend our interests."

The Northern Command will unify a range of domestic security duties now spread over several military units and services.

General Eberhart, who will also remain leader of Norad, will be responsible in his new job for coordinating the military's response to natural disasters like floods, hurricanes and forest fires, officials said.

The new command would also oversee a unit known as the Joint Task Force Civil Support, which is trained to respond to attacks that involve chemical, biological or nuclear weapons.

While the command will have specific defensive responsibilities, like flying combat patrols over American cities, General Eberhart's mission will also involve the delicate task of backing up civilian agencies in time of need.

"We will respond in support of a lead federal agency, such as the F.B.I. or FEMA," he said. "There will be certain things you can do with federal troops and certain things you cannot. There are some situations where there's no other alternatives, and federal forces have to be used to secure the safety and security of our people."

Mr. Rumsfeld and Gen. Richard B. Myers, the chairman of the Joint Chiefs of Staff, have said that in a catastrophe, the military might help quarantine disaster victims and deal with the water and sanitation needs of thousands of people.

"If a city had no ability to respond and no ability to command and control, there's a situation where the president says: `This is an emergency. Northern Command, you have the lead,' " General Eberhart said. "God forbid, we'd be prepared to do that."