WASHINGTON — The director of the National Security Agency says he wants to provide as much public detail as possible on the agency's surveillance programs, arguing that they protect America while also guarding the public's civil liberties and privacy.

NSA director Keith Alexander told senators at a hearing Wednesday that he doesn't want to jeopardize national security but wants a public debate about the phone and email surveillance programs disclosed last week by a former NSA contractor.

Alexander was questioned at length by senators seeking information on exactly how much data the NSA collects and the legal backing for the activities.

He warned that disclosure of the secret programs will erode agency capabilities and, as a result, U.S. allies and Americans won't be as safe as they were two weeks ago.