AP Photo/J. Scott Applewhite

Brennan had a sharp exchange with with Idaho Republican Sen. James Risch, who suggested that Brennan had himself compromised national security when he briefed reporters about last year's foiled al-Qaeda plot to smuggle bombs aboard commercial airliners.

The Obama administration had been angered by media reports last May that revealed the plot and inadvertently compromised a Saudi undercover agent who had penetrated the al-Qaeda cell and obtained the bomb before the terrorists could use it. 

But Risch suggested that Brennan had helped the terrorists by revealing publicly that the bomb was under U.S. control. Brennan had made the comment to reassure air passengers after the bomb plot was made public.

"I think the leak is right in front of me," said Risch, accusing the CIA nominee of alerting al-Qaeda to the successful foiling of the plot.

"I disagree with that vehemently, " Brennan snapped. He told the committee that he was a "witness, not a target" in a Justice Department investigation into the leak about the bomb threat.