Via the detailed review at The Road to Surfdom, a quotation from Richard Clarke’s Against All Enemies:
By the afternoon on Wednesday [September 12, 2001], Secretary Rumsfeld was talking about broadening the objectives of our responses and “getting Iraq.” Secretary Powell pushed back, urging focus on al Qaeda. Relieved to have some support, I thanked Colin Powell and his deputy, Rich Armitage. “I thought I was missing something here,” I vented. “Having been attacked by al Qaeda, for us now to go bombing Iraq in response would be like our invading Mexico after the Japanese attacked us at Pearl Harbour.”