President Barack Obama's choice to head the CIA, John Brennan, says the United States uses drone strikes against terror suspects overseas only to deter an attack and not to punish earlier attacks.
Brennan defended the controversial U.S. policy during his conformation hearing Thursday before the Senate Intelligence Committee.
Unmanned drones have killed U.S. citizens suspected of involvement in terrorism. Civil libertarians say it is like sentencing an American to death without a fair trial.
Brennan, who is Mr. Obama's top counterterrorism advisor, said the U.S. is at war with al-Qaida. He said the United States has a rigorous process of deciding when to use lethal force and that such action is backed by the law. He said the decision to kill a suspect is a last resort where there is no alternative and when there is an imminent threat of terrorism.
Protesters briefly interrupted the hearing several times. The proceedings were stopped and spectators were told to leave.
Brennan said while he was with the CIA when George W. Bush was president, he was aware that a form of extreme questioning called waterboarding was being used to extract information from terror suspects. He said he did not like the practice and thought it would fail, but did nothing to stop it.
Brennan told the senators if he is confirmed, he would be non-partisan. He said he would not tell the president what he wants to hear, but what he needs to hear.