WASHINGTON — The FBI is significantly expanding intelligence gathering in the United States, including stepped-up efforts to collect and report intelligence on foreign figures and governments, a function long the principal domain of the CIA, sources said yesterday.

Last month the bureau began discussions with top officials of the CIA to rewrite the 20-year-old ground rules covering how the agencies conduct their intelligence efforts in the United States and abroad.

That reflects an acceleration of the FBI's foreign-intelligence collection efforts in the United States in recent months and the desire of top bureau officials to assert what they view as their legal duty to track CIA activities in the United States and coordinate with agency operations.

The moves are causing concern among some current and former CIA officials, who see it as another sign of the diminished standing of the embattled agency, which also is confronted by recent Pentagon moves to increase its military-intelligence collections abroad.

The CIA was singled out for harsh treatment by the Sept. 11 commission and is undergoing a painful restructuring under new leadership. Some worry that new CIA Director Porter Goss is not doing enough to fight off the bureau's push.

"This is the kind of thing that the [director of central intelligence] ought to be standing up on his hind legs and making a fuss [about]," said a former senior CIA official. "This is a battle for survival."

Other agency officials say those concerns are overblown. A CIA spokesman declined comment.

Officials familiar with the FBI's thinking are hoping a tentative draft of the new procedures — which are classified — will be completed next month; they said the bureau also hopes to obtain new assurances that the CIA will share information about its U.S. activities with the FBI.

Just months ago, members of Congress were debating whether to strip the bureau of its ability to conduct intelligence functions at all after widespread bungling and intelligence failures in the months preceding Sept. 11, 2001.

"The FBI has an obligation to step up to the plate and use its resources," a former U.S. official sympathetic to the bureau said. "The FBI always had the mandate to collect information on foreign governments within the boundaries of the U.S. [But] there was never an enterprisewide intelligence capability to ensure that."

Now, the former official pointed out, the bureau is rapidly attempting to build one, hiring hundreds of intelligence analysts and other specialists and setting up groups in field offices whose sole mission is to collect and report intelligence.

The interest in foreign intelligence resulted partly from what the bureau views as successes from interviews about possible terrorist threats it conducted with Iraqi Americans in the United States in the run-up to the Iraq war. Officials say the interviews produced information that saved the lives of U.S. soldiers in combat.

It also reflects an aggressive new vision promulgated by the bureau's intelligence czar, Maureen Baginski, a Russian linguist and career intelligence analyst whom FBI Director Robert Mueller hired away from the National Security Agency two years ago.

The result, one former official said, has been an "exponential" growth in recent months in the number of intelligence reports the bureau has circulated.

While the CIA is principally responsible for overseas intelligence collection, it has domestic stations in most major U.S. cities.

Some current and former CIA officials said they believe the bureau is angling to take control of such long-established tasks of CIA stations as recruiting foreign travelers and U.S. businesspeople who visit countries of interest to the intelligence community, and cultivating and managing U.S. business relations overseas.

They also said FBI officials want to take over production and distribution of intelligence reports based on information from such domestic sources in what they assert is a statistics-padding move that could help the FBI compete for funding and resources, at the CIA's expense. "We're in a numbers game," said one intelligence official familiar with the proposals. "And the FBI is trying to establish themselves as somebody who can produce a lot of IIRs [intelligence information reports]."

But people close to the bureau say that officials there have no interest in treading on the CIA's turf and that the FBI is interested in cooperation rather than competition. "There is more than enough work to go around," said a person familiar with the FBI's plans.