The Central Intelligence Agency is expanding its domestic presence, placing agents with nearly all of the FBI's 56 terrorism task forces in U.S. cities, a step that law enforcement and intelligence officials say will help overcome some of the communications obstacles between the two agencies that existed before the Sept. 11, 2001, attacks.

In many cities, according to local FBI special agents, the CIA employees help plan daily operations and set priorities, as well as share information about suspected foreigners and groups. They do not, however, take part in operations or make arrests.

FBI Director Robert S. Mueller III recently described the new arrangement as his answer to MI5, Britain's internal security service. Unlike the CIA, MI5 is empowered to collect intelligence within Britain and to act to disrupt domestic threats to British national security. "It goes some distance to accomplishing what the MI5 does," Mueller told a House-Senate intelligence panel last week in describing the new CIA role in the FBI task forces.

Separately, the CIA is undertaking what one intelligence official called a "concerted effort" to increase the number of case officers working in the agency's domestic field offices. Those offices, directed by the National Resources Division, are staffed by officers from the clandestine service.

The CIA's domestic field offices recruit foreigners living temporarily in the United States -- for example, scientists at universities, diplomats at embassies and business executives -- to work as agents for the CIA when they return home. They also conduct voluntary debriefings of Americans, mainly business executives and academics, who have recently returned from abroad. The division also is responsible for handling some defectors and for limited counterintelligence targeting.

In the mid-1980s, the agency maintained close to 35 field stations in the United States. But over the last decade, budget cuts and operational restrictions reduced the agency's domestic effort by about 30 percent, according to one former high-ranking CIA official. "They were in bad shape."

Since Sept. 11, the National Resources Division has been given more money and some of its domestic offices have been reopened to bring the number close to 30. "There is a concerted effort to enhance that," said one administration official said.

The CIA's domestic division was created in 1963 to conduct clandestine operations within the United States against foreign targets, usually foreign spies and organizations. But the CIA no longer conducts clandestine operations at home, in part because of the 1973 intelligence overhaul that curbed spying on U.S. citizens and enacted stricter oversight of covert operations. Since then, too, the FBI has strictly limited the information it accepts from the CIA, for fear of "tainting" ongoing domestic investigations with information it is not allowed to use or, in some cases, even possess.

While the new growth in the CIA's domestic work does not involving spying, it does represent a significant step in integrating the CIA's analytical capabilities with U.S. law enforcement efforts to find and apprehend terrorist suspects.

"We are stepping into an area that is fraught with peril," said Frederick Hitz, a former inspector general at the CIA. But Hitz and other analysts applauded the effort.

The CIA's work on the FBI task forces "is a sign of the times," said Sen. Bob Graham (D-Fla.), chairman of the Senate intelligence committee. "The idea is to get all the intel and law enforcement agencies that might be able to contribute to a coherent and comprehensive plan against terrorist activities."

None of the growth in the CIA's domestic work has required changes in law.

Under Executive Order 12333, signed by President Ronald Reagan, the CIA is permitted to secretly collect "significant" foreign intelligence within the United States if the collection effort is not aimed at the domestic activities of U.S. citizens and corporations.

Ellen Knowlton, the special agent in charge of the FBI's Las Vegas field office, called the CIA officers in her office "full and active participants" in day-to-day operations. The exchange of ideas among the FBI, the CIA and local law enforcement "is very interactive," she said.

"You balance how you use them" with the potential for compromising officers still under cover, said Joseph Billy Jr., special agent in charge of the FBI's New York field office. "We reserve the right for the CIA to make that call."

For this reason, the identities of CIA officers are often not shared with local law enforcement officials who are detailed, part-time, to work on the task forces. The CIA officers also usually work in special parts of the larger task force building, behind walls impenetrable to electronic eavesdropping.

In Oregon, Portland Police Chief Mark Kroeger said there remains a deep distrust toward giving law enforcement or the CIA expanded powers. Although he approves of the CIA presence, he said he purposefully stays clear of the CIA officers.

"I know very little about them and I chose to keep it that way," he said. "The CIA is not a dirty word," he said. "They have roles and responsibilities that certainly have shifted. I have a lot of admiration for the organization."

While the CIA presence is new in many cities, the agency has worked with local police departments for years in New York, New Jersey and a handful of other locations. The New York joint terrorism task force of 300 people from 21 agencies has had more a dozen CIA officers for years.

The CIA is reluctant to talk about its new task force role, or its domestic field offices. "This increased cooperation is critical in the fight against terrorism," said CIA spokesman Mark Mansfield. "It's critical to establish more and better linkages."