Vice President Joseph R. Biden Jr. (right) and Defense Secretary Leon E. Panetta participate in a commemorative ceremony on the 10th anniversary of the Sept. 11 attacks at the Pentagon in Washington on Sunday, Sept. 11, 2011. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

Vice President Joseph R. Biden Jr. (right) and Defense Secretary Leon E. Panetta participate in a commemorative ceremony on the 10th anniversary of the Sept. 11 attacks at the Pentagon in Washington on Sunday, Sept. 11, 2011. (AP Photo/Charles Dharapak)