In a round of television appearances, Gonzales provided a more detailed legal rationale for Mr. Bush's decision authorizing the National Security Agency to eavesdrop on international phone calls and e-mails of people within the United States without seeking warrants from courts.
Gonzales said he had begun meeting with members of Congress on the Bush administration's view that Congress' authorization of the use of military force after the Sept. 11, 2001 attacks was ample authorization for the surveillance.
"Our position is that the authorization to use military force which was passed by the Congress shortly after Sept. 11 constitutes that authority," Gonzales said on CBS News' The Early Show.
It was the most detailed legal explanation given by an administration official since the New York Times reported Thursday that since October 2001 Mr. Bush had authorized the NSA to conduct the surveillance.
Gonzales said Congress' action after Sept. 11 essentially "does give permission for the president of the United States to engage in this kind of very limited, targeted electronic surveillance against our enemy."
The domestic spying revelations have outraged members of Congress, with Democrats and Republicans alike calling for an investigation.
The president has, I think, made up a law that we never passed," said Sen. Russell Feingold, D-Wis.
Sen. Arlen Specter, R-Pa., chairman of the Senate Judiciary Committee, said he intends to hold hearings.
"They talk about constitutional authority," Specter said. "There are limits as to what the president can do."
Senate Democratic Leader Harry Reid of Nevada also called for an investigation, and House Democratic leaders asked Speaker Dennis Hastert to create a bipartisan panel to do the same.
President Bush, in a rare live address, said congressional leaders have been apprised of the secret order "more than a dozen times."
First Amendment legal expert Floyd Abrams told CBS News correspondent Randall Pinkston the president is attempting to mitigate his sidestepping of Congress by saying he had informed some lawmakers.
"It is mitigated in the sense that Congress was not completely uninformed," Abrams said. "As a legal matter though, what the president has authorized 30 times may have been illegal 30 times."
"It's been briefed to the Congress over a dozen times, and, in fact, it is a program that is, by every effort we've been able to make, consistent with the statutes and with the law," Vice President Dick Cheney said Sunday in a televised interview to be broadcast Monday evening: "It's the kind of capability if we'd had before 9/11 might have led us to be able to prevent 9/11."
Sen. John McCain, R-Ariz., said there were no objections raised by lawmakers who were told about it.
"That's a legitimate part of the equation," McCain said. But he said President Bush still needs to explain why he chose to ignore the law that requires approval of a special court for domestic wiretaps.
"The president can't pass the buck on this one. This is his program," Reid said. "He's commander in chief. But commander in chief does not trump the Bill of Rights."
House Minority Leader Nancy Pelosi, D-Calif., said in a statement Saturday that she had been told on several occasions about unspecified activities by the NSA. Pelosi said she expressed strong concerns at the time.
Secretary of State Condoleezza Rice said on "Fox News Sunday" that Mr. Bush "has gone to great lengths to make certain that he is both living under his obligations to protect Americans from another attack but also to protect their civil liberties."
Several lawmakers weren't so sure. They pointed to a 1978 federal law, the Foreign Intelligence Surveillance Act, which provides for domestic surveillance under extreme situations, but only with court approval.
Specter said he wants Mr. Bush's advisers to cite their specific legal authority for bypassing the courts. The president said the attorney general and White House counsel's office had affirmed the legality of his actions.
Appearing with Specter on CNN's "Late Edition," Feingold said Mr. Bush is accountable for the program regardless of whether congressional leaders were notified.
"It doesn't matter if you tell everybody in the whole country if it's against the law," said Feingold, a member of the Judiciary Committee.
Mr. Bush said the program was narrowly designed and used in a manner "consistent with U.S. law and the Constitution." He said it targets only international communications of people inside the U.S. with "a clear link" to al Qaeda or related terrorist organizations.
Government officials have refused to define the standards they're using to establish such a link or to say how many people are being monitored.
Sen. Lindsey Graham, R-S.C., called that troubling. If Mr. Bush is allowed to decide unilaterally who the potential terrorists are, he in essence becomes the court, Graham said on Face the Nation.
"We are at war, and I applaud the president for being aggressive," said Graham, who also called for a congressional review. "But we cannot set aside the rule of law in a time of war."
The existence of the NSA program surfaced as Mr. Bush was fighting to save the expiring provisions of the Patriot Act, the domestic anti-terrorism law enacted after the Sept. 11 attacks.
Renewal of the law has stalled over some its most contentious provisions, including powers granted law enforcement to gain secret access to library and medical records and other personal data during investigations of suspected terrorist activity.
Democrats have urged Mr. Bush to support a brief extension of the law so that changes could be made in the reauthorization, but Bush has refused, saying he wants renewal now.