The Bush administration, in its fight against terrorism, is slowly chipping away at the wall that has existed for nearly three decades between domestic law enforcement and international intelligence gathering in an effort that senior officials said was vital to waging war against Al Qaeda and other terror networks.

The barrier between domestic and overseas intelligence gathering was erected when the Central Intelligence Agency was created in 1947. It was significantly hardened in the 1970's in response to Congressional investigations that produced revelations of widespread abuses by the Federal Bureau of Investigation and the intelligence agency.

But since the attacks on New York and the Pentagon, the Bush administration has waged a different kind of war, mostly under the existing rules. Now, senior government officials have concluded that the changes made so far have not addressed the fundamental flaws of the old rules, leaving the United State still vulnerable to terrorists.

The changes are coming about in part because of Congressional criticism of the performances of the F.B.I. and C.I.A. before the terrorist attacks on New York and Washington. The two agencies will also be under the scrutiny of an independent commission created this week to examine their activities before the attacks.

The administration and Congress had already been reviewing ideas to overhaul intelligence and law enforcement that have been considered untouchable for a generation.

One is the creation of a domestic espionage agency; another is the use of the military in United States law enforcement. There is no agreement yet on new structures or whether the basic mandates and core operations of the central agencies will be changed.

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