Facing angry criticism and challenges to his authority in Congress, President Bush on Saturday unapologetically defended his administration's right to conduct secret post-Sept. 11 spying in the United States as "critical to saving American lives." House Minority Leader Nancy Pelosi, D-Calif., said she had been told on several occasions that Bush had authorized unspecified activities by the National Security Agency, the nation's largest spy agency. She said she had expressed strong concerns at the time, and that Bush's statement Saturday "raises serious questions as to what the activities were and whether the activities were lawful." "The activities I have authorized...