ASHINGTON, May 6 — A top Pentagon research official told Congress today that a program intended to forestall terrorism by tapping computer databases — but curbed by legislation this winter because of privacy fears — would not look into Americans' financial or health records.

Instead, the official said the program, the Total Information Awareness program, would rely mostly on information already held by the government, especially by law enforcement and intelligence agencies.

The Pentagon official, Dr. Tony Tether, director of the Defense Advanced Research Projects Agency, also known as Darpa, told a House Government Reform subcommittee that "we are not developing a system to profile the American public."

Dr. Tether offered a vision of the program that sounded much less threatening than the description given last year by John M. Poindexter, the retired admiral who is in charge of the project.

Mr. Poindexter told a California audience then that "we must become much more efficient and more clever in the way we find new sources of data, mine information from the new and old, make it available for analysis, convert it to knowledge and create actionable options." He described a system that could tap into Internet mail, culling records, credit card and banking transactions and travel documents.

Dr. Tether said he hoped that the agency's impending report on the project, due on May 20, would calm public and Congressional fears.

In February, legislation prohibiting deployment of the system said that research could not continue after May 20 unless the agency provided Congress a detailed description of the project, from its spending plans to its impact on privacy and civil liberties to its likelihood of trapping terrorists.

Today, under friendly questioning by Representative Adam H. Putnam, a Florida Republican who is the subcommittee's chairman, Dr. Tether said the main area of private data that might be useful in anticipating terrorist attacks would be transportation records, since terrorists had to travel.

Saying "I'm trying to help you guys a little with your p.r. problem," Mr. Putnam invited Dr. Tether to swear that the agency was not "contemplating" using credit card, library or video-rental information. Dr. Tether said he could see no value in any such data, but he could not swear that no consultant hired by the agency was not "contemplating" the value.

Dr. Tether said the system was intended to devise "attack scenarios" based on past terrorist attacks or intelligence about plans.

He offered two examples. If the concern was a truck bomb, he said, one question to be posed was, "Are there foreign visitors to the United States who are staying in urban areas, buying large amounts of fertilizer and renting trucks?"

Or, he said, if the system had been in place, it could have considered the threat posed by a 1995 report from the Philippines that terrorists were considering using airplanes as bombs to destroy landmarks like the World Trade Center.

Hypothesizing about how that would be accomplished, he said, a review of that report would suggest that terrorists would have to learn how to fly large planes, without focusing on how to land them. That issue might have triggered more attention to F.B.I. concerns in Phoenix in 2001 about foreigners taking flying lessons, he said.

Dr. Tether argued that from the outset of the Total Information Awareness project, Darpa had been aware of the need to protect privacy. One essential element was concern by different agencies that sources of their information be kept secret. "Historically," he said "agencies have been reluctant to share intelligence data for fear of exposing their sources and methods."

But he also said his agency intended the tools it developed "to be only used in a manner that complies with the Privacy Act."

Dr. Teher said that, "We knew that the American public and their elected officials must have confidence that their liberties will not be violated before they would accept this kind of technology."