Snow defended the newly disclosed program, saying it was an effective tool in tracking the financial operations of terrorists.
``By following the money we've been able to locate operatives, we've been able to locate their financiers, we've been able to chart the terrorist networks, and we've been able to bring the terrorists to justice," he said.
``If people are sending money to help Al Qaeda, we want to know about it," Snow said.
He said Congress had been briefed on the program.
At the White House, presidential spokesman Tony Snow said the focus had been on shutting off terrorist financing.
``It's a good thing to shut off the spigot, the financial spigot," he said. ``It does seem to be working."
In the weeks following the Sept. 11 attacks, Treasury officials obtained access to an extensive international financial data base -- the Society for Worldwide Interbank Financial Telecommunication .
The cooperative, based in Belgium, handles financial message traffic from thousands of financial institutions in more than 200 countries.
``It's important to understand that very significant protocols and safeguards have been put in pace in a cooperative way between Swift and the Treasury Department," Snow said.
He said that access to the data that had been collected was limited to people with security clearances.
Snow declined to give specific examples of where the program had been successful in shutting off terrorist financing, but said that he had assured himself that it was working.
The administration had used broad subpoena powers to get access to that data.
In a statement, the worldwide interbank society said that it had negotiated with the US Treasury ``over the scope and oversight of the subpoenas."
Disclosure of the program comes on the heels of intense controversy over President Bush's ordering of National Security Agency surveillance of telephone calls and e-mails of private citizens.
