NSA under 'rigorous' oversight, chief says

The head of the US National Security Agency said Wednesday the top-secret unit operates under "strict guidelines" and "rigorous oversight" as he faced lawmakers about revelations of a vast surveillance program.

"We operate in a way that ensures we keep the trust of the American people because that trust is a sacred requirement," General Keith Alexander said in prepared testimony. "We do not see a tradeoff between security and liberty."

Alexander's prepared remarks did not specifically address revelations about the PRISM program, described as a wide-ranging system of surveillance in coordination with major Internet companies, but it was his first appearance before Congress since the explosive revelations last week.

Alexander, director of the secretive NSA and chief of the military's Cyber Command, said these and other government agencies are "deeply committed to compliance with the law and the protection of privacy rights," even though details of the operations are classified.

"Given the nature of our work, of course, few outside of our executive, legislative and judicial branch oversight bodies can know the details of what we do or see that we operate every day under strict guidelines and accountability within one of the most rigorous oversight regimes in the US government," he said in remarks prepared for a Senate panel.