Pentagon marks anniversary of 9/11 dead

Vice President Joe Biden, accompanied by the Defence Secretary and top US military officer, led a somber tribute Sunday to the 184 victims of the September 11 attack on the Pentagon a decade ago. Admiral Mike Mullen, the chairman of the joint chiefs of staff, and Defense Secretary Leon Panetta said Al-Qaeda caused tragedy but that the US military had become stronger since 9/11, meting out justice and strengthening its resolve. Duration: 01:06