President Acknowledges Approving Secretive Eavesdropping

"The activities I have authorized make it more likely that killers like these 9/11 hijackers will be identified and located in time," he said.

Bush said the program is reviewed every 45 days by the attorney general and White House counsel and that he must then reauthorize it to keep it active. He said he has reauthorized it more than 30 times "and I intend to do so for as long as our nation faces a continuing threat from al Qaeda and related groups."

The president also said the administration has briefed key members of Congress on the program a dozen times. Classified programs are typically disclosed to the chairmen and ranking minority members of the House and Senate intelligence committees.

Bush justified his order on his presidential powers as commander in chief as well as his interpretation of the congressional resolution authorizing him to use force in response to the Sept. 11 attacks, passed days after the World Trade Center and the Pentagon were hit. But Bush did not explain his constitutional thinking, nor how the 2001 resolution gave him the authority to order domestic spying. He took no questions, and aides would not discuss the legal issues surrounding the program.

The NSA surveillance is the latest chapter in a growing political struggle over the contours of the administration's tactics against terrorism. Two days ago, Sen. John McCain (R-Ariz.) forced Bush to accept a new law explicitly outlawing the use of cruel, inhuman and degrading treatment of prisoners. Several senators are pressing the administration to provide information on secret CIA detention facilities overseas. And the debate over the Patriot Act centers on how far law enforcement can go in trying to find terrorist plots.

The president criticized the media for reporting on the NSA surveillance as well as the officials who "improperly" provided the information. "As a result, our enemies have learned information they should not have, and the unauthorized disclosure of this effort damages our national security and puts our citizens at risk," he said.

The White House decision to confirm the program was an extraordinary move by an administration that almost never publicly discusses such classified methods adopted in its battle against terrorism. The administration, for instance, has never publicly discussed the existence of secret CIA prisons in Eastern Europe even after they were reported in The Post.

But in this case, with the Patriot Act renewal on the line, the president's advisers calculated that they should go on the offensive. "This directly takes on the Democrats and puts them in a box -- support our efforts to protect Americans or defend positions that put our nation's security at greater risk," said a senior administration official, who spoke on condition of anonymity to discuss political strategy. "We are confident most Americans support the president's actions."

Bush's confirmation of the NSA order, on the other hand, could embolden congressional critics to explore the extent of the program.

Senate Judiciary Chairman Arlen Specter (R-Pa.) has already called such surveillance "inappropriate" and vowed to conduct hearings. It may prove harder for the administration to withhold information now that the president has publicly acknowledged its existence.

Staff writers Charles Babington and Barton Gellman contributed to this report.