WASHINGTON, D.C. -- The Republican chairman of the Senate Judiciary Committee is warning the White House that he may introduce legislation to cut off funding for the secret National Security Agency wiretapping program if the Bush administration does not respond to his questions about the matter.

Senator Arlen Specter of Pennsylvania expressed his frustration that the Bush administration has not given him satisfactory answers about the wiretapping program, established after the September 11, 2001 terrorist attacks.

"So far we have seen no willingness on the part of the attorney general or the Department of Justice or the White House to do very much," said Arlen Specter.

The program allows for warrantless eavesdropping on international phone calls and e-mails between people in the United States and suspected terrorists overseas. It bypasses a special federal court whose approval is required under law for domestic wiretapping operations.

Although President Bush has insisted the program is within his authority, Senator Specter remains skeptical.

"The program may be constitutional, but we do not know that because we do not know what the program is," he said.

At a Capitol Hill news conference, Specter threatened to withhold funding for the program in an effort to press the administration to be more forthcoming.

"It is possible that the only way that the Congress can assert its constitutional prerogative may be through the exercise of the power of the purse, which is a drastic remedy on which I am not prepared to support at the moment, but one which may have to be considered if there is no other way for Congress to assert its constitutional prerogatives," noted Senator Specter.

Specter said he believed that any new laws passed by Congress to increase the legislative branch's oversight of the program could be ignored by the administration in the name of national security.

He said he raised his concerns about the program directly to President Bush at a White House meeting with other senators this week. He said the President listened but, in his words, did not take the opportunity to engage him.