According to The New York Times, the role includes operations targeting so-called terror groups and those involved in weapons proliferation.
Some of the intelligence areas in which the Pentagon hopes to become more involved include operations that have traditionally been the province of the Central Intelligence Agency (CIA), the Times said on Sunday.
The details of the plan remain secret and are still being refined, but among the ideas cited by defence department officials is that of fighting for intelligence or launching combat operations to obtain intelligence, according to the newspaper.
Bush administration officials said the proposals, the latest in a long-standing rivalry between the Pentagon and the CIA over intelligence, were being monitored and had not yet won White House approval.
Intelligence officials describe the proposal as an attempt by the Pentagon to expand its intelligence gathering operations, just as President George Bush signed legislation on Friday enacting broad changes in US intelligence operations, the Times said.
The legislation creates a new spy director to oversee the country's 15 intelligence agencies as demanded after the 11 September 2001 attacks, a move some Pentagon chiefs feared could interfere with the military chain of command.
Spies and policymakers
Another facet of the plan is a major expansion of the collection of intelligence for the Pentagon by spies, including more aggressive missions aimed at acquiring specific intelligence sought by policymakers.
A major shift in the Pentagon's plan would be to focus military intelligence operations more on counterterrorism and counterproliferation, areas in which the CIA has always played the leading role.
The Pentagon plan would take on
some CIA intelligence operations
"Right now we are looking at providing special operations forces some of the flexibility the CIA has had for years," the Times quoted a defence department official as saying, on condition of anonymity.
"It would be used judiciously, and with all appropriate oversight controls."
Other components of the plan, which has been under review at the Pentagon since January, include revamping military commands to ensure that senior officers planning and fighting wars work more closely with the intelligence analysts tracking threats such as terrorists and insurgency cells, the Times said.