Disclosure of a secret program giving the U.S. government access to a massive international data base of financial information was "very damaging" to efforts to catch terrorists, Congress was told Tuesday.

"This disclosure compromised one of our most valuable programs and will only make our efforts to track terrorist financing — and to prevent terrorist attacks — harder," Stuart Levey, undersecretary for terrorism and financial intelligence at the Treasury Department, argued before a House Financial Services panel.

The program, started shortly after the Sept. 11, 2001, terror attacks, generated lots of leads, Levey said. But he added that details remain classified.

Levey said the program played an important role in an investigation that eventually led to the capture of Indonesian Riduan Isamuddin, or Hambali, the operations chief of the Al Qaeda linked Jemaah Islamiya, a Southeast Asian terror group. Hambali allegedly masterminded the deadly 2002 Bali bombings.

Both Republicans and Democrats on the panel — which has oversight over financial matters — expressed concern that they weren't briefed early on about the program.

Rep. Sue Kelly, R-N.Y., chairwoman of the House panel, asked Congress's investigative arm, the Government Accountability Office, to conduct a probe of the program to make sure it was conducted properly in accordance with the law.

Kelly called her request for a GAO investigation "mere due diligence" to make sure "our trust is not poorly placed in the Treasury Department." She also asked for the administration to provide the panel with a closed-door, classified briefing about the program.

Rep. Carolyn Maloney, D-N.Y. complained that the Bush administration "has kept Congress in the dark" by not informing her colleagues on the panel about the program years ago.

The terror tracking program was first publicly revealed late last month in published accounts by the New York Times, Los Angeles Times and Wall Street Journal.

The revelation stirred some concern among privacy advocates and some Democrats. But it angered President Bush and administration officials who asserted that it could hobble their efforts to shut down avenues for terrorist fundraising.

Asked whether the government is investigating the disclosure or leak of the program, Levey said the Treasury Department is in consultations with the Justice Department about the appropriate way to go forward.

The government was able to assess the immense data base, operated by a Belgium-based consortium and known by the acronym SWIFT — for the Society for Worldwide Interbank Financial Telecommunication — only through subpoenas.

"The SWIFT subpoena is powerful but narrow," Levey said. "We cannot simply browse through the records that Swift turns over — we are only able to see the information which is responsive to targeted searches in the context of a specific terrorism investigation," he said.

A record is kept of every search conducted, he noted. These records are reviewed by Swift's representatives and an outside, independent auditor, he said.

"I want to emphasize that we cannot search this data for evidence of non-terrorist-related crime, such as tax evasion, economic espionage, money laundering or other criminal activity," Levey told the panel. "As a result we have accessed only a minute fraction of the data that Swift has provided."

Swift handles financial message traffic from thousands of financial institutions in more than 200 countries. The service routes more than 11 million messages each day, mostly capturing information on wire transfers and other methods of moving money in and out of the United States.

When asked whether the program is effectively dead because of the revelations of its existence, Levey responded: "It remains to be seen."