The move is sparking concern among civil liberties advocates and those who fear an encroaching military role in domestic law enforcement.

In an argument that eerily foreshadowed the July London terror attacks, the Pentagon in late June announced its "Strategy for Homeland Defense and Support," which would expand its reach domestically to prevent "enemy attacks aimed at Americans here at home."

The strategy, approved by Deputy Defense Secretary Gordon England (search ) on June 24, argues that the government needs a multi-layered, preventive approach to national defense in order to combat an unconventional enemy that will attack from anywhere, anytime and by any conceivable means.

"Transnational terrorist groups view the world as an integrated, global battlespace in which to exploit perceived U.S vulnerabilities, wherever they may be," reads the 40-page document that outlines the new plans.

"Terrorists seek to attack the United States and its centers of gravity at home and abroad and will use asymmetric means to achieve their ends, such as simultaneous mass casualty attacks," it said.

Critics say the fears raised by the Pentagon are being used as a justification for the military to conduct wider, more intrusive surveillance on American citizens.

"Do we want, as a free people, with the notion of privacy enshrined in the Constitution and based on the very clear limits and defined role of government, to be in a society where not just the police, but the military are on the street corners gathering intelligence on citizens, sharing that data, manipulating that data?" asked former Rep. Bob Barr (search ), R-Ga., a constitutional law expert and civil libertarian.

"This document provides a blueprint for doing just that."

Barr said the new strategy is a back-door means of following through with a 2002 plan to create a massive, centralized information database using public and private records of individuals, called "Total Information Awareness." Congress killed TIA in 2003 because of civil liberties and privacy concerns.

Critics say they believe much of TIA lives on in some form through smaller, undisclosed military contracts. This latest plan, they say, is one way of jump-starting TIA's initial goals.

"This is TIA back with a vengeance," said Barr. "What they have come up with here is a much vaguer and much broader concept that sounds more innocuous. [The Pentagon] is getting much smarter in how to sell these things."

The Defense Department report says its increased surveillance capabilities at home will adhere to constitutional and privacy protections, even though it emphasizes enhancing current "data mining" capabilities.

"Specifically, the department will… develop automated tools to improve data fusion, analysis, and management, to track systematically large amounts of data and to detect, fuse and analyze aberrant patterns of activity, consistent with U.S. privacy protections," the report reads.

It will also develop "a cadre of specialized terrorism intelligence analysts within the defense intelligence community and deploy a number of these analysts to interagency centers for homeland defense and counter-terrorism analysis and operations," states the report.

Some national security experts agree that emboldened surveillance on domestic soil is necessary in the global War on Terror, and that such intelligence could prevent the kind of attacks perpetuated by homegrown terrorists in England on July 7 and 21.

"The Defense Department has always done intelligence operations in the United States. They have the legal right to do that. There is nothing new here," James Carafano, a homeland security analyst with The Heritage Foundation, told FOXNews.com. "There are no new threats to privacy or constitutionality. I just think it's about doing [intelligence] more efficiently and effectively."

But John Pike, founder of GlobalSecurity.org , a clearinghouse of available intelligence and national security information, says it's not so clear how much data the Pentagon will be collecting on citizens and whether it will be retaining, sharing and building individual dossiers. So far, the lack of detail leaves as many question as answers, he said.

"The bad news is there is certainly the possibility of a return to the sort of domestic surveillance that we saw in the 1950s and 1960s," Pike said.

Pentagon officials declined to comment on the variety of data it would gather and share, or how long it would retain files on individuals under the new homeland defense plan.

The Washington Post reported recently that among the databases being built by the Pentagon is a military recruitment list of individual high school and college students culled from commercial data brokers and other sources. The military is planning to share the database with federal and state law enforcement agencies if necessary, the Post reports.

A Defense Department spokesman said the military's domestic role in homeland security will remain a supportive one, and the Pentagon will only provide resources when local, state and federal resources and capabilities "have been exceeded or do not exist."

"We have expanded activities in order to better execute support missions, but we are extremely sensitive to the historically restricted, limited role of the Defense Department," the spokesman told FOXNews.com in an e-mailed response to questions.

The Pentagon's new strategy appears to dovetail with a recent report by The New York Times, that said the upcoming Quadrennial Defense Review, which outlines the future vision of the military and is due to Congress in February, will reflect a new approach in which the Defense Department will prepare to fight in one war theater at a time while putting the bulk of its resources into homeland defense.

The strategy approved by military officials in June also increases joint training exercises with first responders and other agencies as well as the creation of National Guard-staffed teams in case of a catastrophic attack.

The president would have to authorize the actual use of troops on military soil in order to adhere to the 1878 Posse Comitatus Act, which prohibits military involvement in domestic law enforcement. Pentagon officials say the new strategy won't require that authorization.

But the strategy does includes more collaboration with law enforcement in "support" roles on all levels of counter-terrorism efforts as well as the monitoring of terrorist threats along the borders, in the air and on water.

"If they find information in the course of their business that might help other agencies, then they can share it. If other agencies in their own intelligence gathering find information that can help the Defense Department, they can share that," said Carafano. "I really don’t see any legal or constitutional issues here."