Justice document gives green light for interrogation violence

"We start with the least harsh measures first," Townsend told CNN television. "It stops ... if someone becomes cooperative."

She said the White House was "baffled" by suggestions that if the US government didn`t use harsh interrogation tactics, Al-Qaeda would treat captured Americans better.

And she suggested the harsh interrogation techniques had support and understanding of the American public.

"If Americans are killed because we failed to do the hard things, the American people would have the absolute right to ask us why," Townsend said.