Updated

Disclosures of widespread data-trawling by the National Security Agency are recent, but top Obama and Bush administration officials have denied repeatedly that the government was collecting caches of phone and Internet materials from American citizens.

Some officials denied in congressional hearings and other public settings that the government was engaged in domestic surveillance. In other cases, they said that the NSA was not engaged in sweeping up massive amounts of information.

President Barack Obama acknowledged the existence of the programs Friday even as he gave the government's standard rationale to ease fears that Americans' privacy rights are being violated.

Obama's comments mark the first time a president has acknowledged the secret operations. They followed media revelations that classified NSA operations collected phone and electronic data from millions of Americans.