Congressional leaders of both parties called for hearings and issued condemnations yesterday in the wake of reports that President Bush signed a secret order in 2002 allowing the National Security Agency to spy on hundreds of U.S. citizens and other residents without court-approved warrants.

Bush declined to discuss the domestic eavesdropping program in a television interview, but he joined his aides in saying that the government acted lawfully and did not intrude on citizens' rights.

"Decisions made are made understanding we have an obligation to protect the civil liberties of the American people," Bush said on "The NewsHour With Jim Lehrer."

Disclosure of the NSA plan had an immediate effect on Capitol Hill, where Democratic senators and a handful of Republicans derailed a bill that would renew expiring portions of the USA Patriot Act anti-terrorism law. Opponents repeatedly cited the previously unknown NSA program as an example of the kinds of government abuses that concerned them, while the GOP chairman of the Senate Judiciary Committee said he would hold oversight hearings on the issue.

"There is no doubt that this is inappropriate," said Sen. Arlen Specter (R-Pa.), who favored the Patriot Act renewal but said the NSA issue provided valuable ammunition for its opponents.

Sen. Dianne Feinstein (D-Calif.), a member of the intelligence and judiciary committees, called the program "the most significant thing I have heard in my 12 years" in the Senate and suggested that the president may have broken the law by authorizing surveillance without proper warrants.

"How can I go out, how can any member of this body go out, and say that under the Patriot Act we protect the rights of American citizens if, in fact, the president is not going to be bound by the law?" she asked.

Officials across the government yesterday declined to publicly acknowledge the presidential order. But they defended, in general terms, the administration's aggressive strategies in attempting to combat terrorism since the Sept. 11, 2001, attacks and said that all programs have been lawful and protective of individual rights.

"Let me just say that winning the war on terror requires winning the war of information," Attorney General Alberto R. Gonzales told reporters. ". . . And so we will be aggressive in obtaining that information, but we will always do so in a manner that's consistent with our legal obligations."

Government officials credited the new program with helping to uncover and disrupt terrorist plots, including plans by Iyman Faris, an Ohio truck driver who pleaded guilty in 2003 to planning to blow up the Brooklyn Bridge. Faris's attorney, David B. Smith, said he and his client were never informed about the NSA surveillance and had presumed that the monitoring of his cell phone had been authorized by a court-issued warrant.

The existence of the NSA domestic surveillance program was reported late Thursday by the New York Times and confirmed by U.S. intelligence and counterterrorism officials.

The Washington Post, citing an informed U.S. official, reported that the NSA's warrantless monitoring of U.S. subjects began before Bush's order was issued in early 2002 and included electronic and physical surveillance carried out by other military intelligence agencies assigned to the task.