WASHINGTON, Aug. 30 — The Bush administration is signaling that it plans to turn again to a legal tool, the “state secrets” privilege, to try to stop a suit against a Belgian banking cooperative that secretly supplied millions of private financial records to the United States government, court documents show.

The suit against the consortium, known as Swift, threatens to disrupt the operations of a vital national security program and to disclose “highly classified information” if it continues, the Justice Department has said in court filings.

A hearing on the suit is scheduled for Friday in federal court in Alexandria, Va.

The “state secrets” privilege, allowing the government to shut down litigation on national security grounds, was once rarely used. The Bush administration has turned to it more than 30 times in terrorism-related cases, seeking to end public discussion of cases like the claims of an F.B.I. whistle-blower and the abduction of a German terrorism suspect.

Most notably, the administration has sought to use the privilege to kill numerous suits against telecommunications carriers over the National Security Agency’s eavesdropping program.