Even Congress doesn't know the extent of the National Security Agency's intrusion into U.S. privacy, Sen. Bob Corker said on Sunday, urging the agency to answer for its programs.

"As the top Republican on Senate Foreign Relations, as you sit here today, do you feel that you actually know what the government is and isn't doing in surveilling Americans?" "Fox News Sunday" host Chris Wallace asked the Tennessee Republican.

"No," Corker replied. " I don't think there are many people that work harder than I do. I'm not on the Intelligence Committee, and obviously they are privy to information that I am not, but absolutely not. And that's why I wrote a letter to the president this week to ask that the head of this organization come in and brief folks from top to bottom."

The director of the NSA should brief lawmakers on each program that's underway, how they are being used and what their intent is, Corker said. Then Congress can help determine what sort of oversight is necessary.

"Look, I appreciate efforts to keep Americans secure," Corker said. "At the same time, this is in front of us, we are not in front of it. ... The American people want to know that those of us who are elected, (Rep.) Eliot (Engel) and I know, understand fully what's happening here. I don't think we do. I would imagine there are even members of the Intelligence Committee themselves that don't fully understand the gamut of things that are taking place."