Brushing aside bipartisan criticism in Congress, Mr. Bush said the program has been effective in disrupting the enemy, while "safeguarding our civil liberties." He said it's done in a way that's consistent with the laws and the Constitution. He also said that as president and commander in chief he has "the constitutional responsibility and the constitutional authority to protect our country."
In a session with reporters in the East Room of the White House, Mr. Bush also called it "inexcusable" that the Senate was blocking renewal of the , portions of which are set to expire at year's end. "In a war on terror we cannot afford to be without this law for a single moment," he said.
The legislation has cleared the House but Senate Democrats have blocked final passage and its prospects are uncertain in the final days of the congressional session.
Mr. Bush spoke a day after , urging patience and declaring that the United States was winning the battle.
In his opening press conference remarks, Mr. Bush said the warrantless spying, conducted by the National Security Agency, was an essential element in the same war on terror. He called the leak of details about the program "shameful."
"It was a shameful act for someone to disclose this important program in a time of war. The fact that we're discussing this program is helping the enemy," he said.
The existence of the program was disclosed last week by The New York Times, triggering an outpouring of criticism in Congress, but an unflinching defense from Mr. Bush and senior officials of his administration.
The president spoke not long after said Congress had given the president authority to spy on suspected terrorists in this country in legislation passed after the attacks of Sept. 11, 2001.
Mr. Bush and other officials have said the program involved monitoring phone calls and e-mails of individuals in the United States believed to be plotting with terrorists overseas.
Normally, no wiretapping is permitted in the United States without a court warrant. But Mr. Bush said he approved the action without such orders "because it enables us to move faster and quicker. We've got to be fast on our feet.
"It is legal to do so. I swore to uphold the laws. Legal authority is derived from the Constitution," he added.