The FBI and CIA are moving their counter-terror operations into a joint complex. The Administration promises that each agency will maintain control over its own staff.

But a joint intelligence center to be created at the same location, probably in Northern Virginia, will report to George J. Tenet, the director of central intelligence. That arrangement in particular has prompted civil liberties advocates to warn that lines of authority could become blurred, giving the Central Intelligence Agency a new role in domestic spying....

Civil liberties advocates said they were concerned that the plan, especially the creation of the joint center with the director of central intelligence in charge, would give the C.I.A. an active role in the gathering of intelligence within the United States.

Timothy Edgar, legislative counsel for the American Civil Liberties Union, said in an interview that despite pledges by the Bush administration to honor the longtime separate roles of the two agencies, "we think it will be difficult for them to hold that line."

Bush has said he intends for the two agencies to maintain their separate identities and operations, but that there is a greater need for sharing of intelligence information.

He said the move was "an important advance" in creating a better, more integrated system for analyzing intelligence about terrorists...."In order to better protect our homeland, our intelligence agencies must coexist like they never had before."

The new center will be called the Terrorist Threat Integration Center. It will open for business May 1.