WASHINGTON - The Bush administration has been quietly tracking people suspected of bankrolling terrorism, using a secret program that gives the government access to a massive data base of international financial transactions.

Treasury Department officials said they used broad subpoenas to collect the financial records from an international system known as Swift. Stuart Levey, Treasury's undersecretary for terrorism and financial intelligence, called the subpoenas “a legal and proper use of our authorities.”

“Since immediately following 9/11, the American government has taken every legal measure to prevent another attack on our country,” Dana Perino, deputy White House press secretary, said. “One of the most important tools in the fight against terror is our ability to choke off funds for the terrorists.”

Under the program, U.S. counterterrorism analysts could query Swift's financial data base looking for information on activities by suspected terrorists as part of specific terrorism investigations, a Treasury Department official said. They would do so by plugging in a name or names, the official said.

The program involved both the CIA and the Treasury Department.

Swift, or the Society for Worldwide Interbank Financial Telecommunication, is a cooperative based in Belgium that handles financial message traffic from 7,800 financial institutions in more than 200 countries.

The service, which routes more than 11 million messages each day, mostly captures information on wire transfers and other methods of moving money in and out of the United States. It doesn't execute these money transfers. The service generally doesn't detect private, individual transactions in the United States, such as withdrawals from an ATM or bank deposits. It is aimed mostly at international transfers.

The administration defended use of the program, saying it plays a vital role in its efforts to identify terrorist financiers.

“Our subpoena of terrorist-related records from Swift has provided us with a unique and powerful window into the operations of terrorist networks,” Levey said.

The existence of the program was first reported Thursday night on the Web sites of The New York Times, the Los Angeles Times and The Wall Street Journal.

While confirming the newspaper reports, both Levey and Perino expressed concern that disclosure of the program could undermine efforts to track terrorism-related activities.

“We know the terrorists pay attention to our strategy to fight them, and now have another piece of the puzzle of how we are fighting them,” Perino said.

The decision to publish was “a tough call; it was not a decision made lightly,” said Doyle McManus, the Los Angeles Times' Washington bureau chief.

Treasury Department officials spent 90 minutes Thursday meeting with the newspaper's reporters, stressing the legality of the program and urging the paper to not publish a story on the program, McManus said in a telephone interview. Swift acknowledged that it complied with the government's subpoenas but said the government's requests were for limited slices of data.