(CNN) -- Secretary of Defense Leon Panetta spelled out the future battle against al Qaeda, praising what has been done so far but warning much more work remains.
Speaking about the September 11 attacks in a speech at the Center for a New American Security, a Washington-based think tank, Panetta said, "We will do everything possible to ensure that such an attack never happens again. That means counterterrorism will continue as a key mission for our military and intelligence professionals as long as violent extremists pose a direct threat to the United States."
He said efforts against the core al Qaeda group have been largely successful. "Al Qaeda's leadership ranks have been decimated. This includes the loss of four of al Qaeda's five top leaders in the last 2½ years alone -- Osama bin Laden, Shaikh Saeed al-Masri, Atiyah Abd al-Rahman and Abu Yahya al-Libi."
But he pointed out that al Qaeda remains a threat outside Afghanistan and Pakistan, in places like Yemen, Somalia and elsewhere.
"We know that al Qaeda, its affiliates and adherents are looking to establish a foothold in other countries in the Middle East and North and West Africa -- including al Qaeda in the Islamic Maghreb and the Boko Haram group in Nigeria. The international community and our regional partners share our concern about Mali, where al Qaeda affiliated groups have taken control of territories in the North and pose an emerging threat. We are also concerned about Libya, where violent extremists and affiliates of al Qaeda attacked and killed innocent Americans in Benghazi," Panetta said.
"With respect to that attack, let me be clear: We will work with the Libyan government to bring to justice those who perpetrated these attacks."
Panetta said the solution to defeating al Qaeda's outlying affiliates is unconventional warfare. "This campaign against al Qaeda will largely take place outside declared combat zones, using a small-footprint approach that includes precision operations."
"We are continuing to ramp up Special Operations Forces, which have doubled in size from 37,000 on 9/11 to 64,000 today. SOF will grow to 72,000 by 2017. We are expanding our fleet of Predator and Reaper UAVs over what we have today."
But he went on to say the real permanent solution to extremist terrorism means more than guns and bombs. "But to truly protect America, we must sustain and in some areas deepen our engagement in the world - our military, intelligence, diplomatic and development efforts are key to doing that."
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