The end of Al Qaeda terrorist network is \"within reach,\" U.S. Defense Secretary Leon Panetta said during his first visit to Afghanistan as Pentagon chief. Panetta, who took over the helm of Pentagon on July 1, made a surprise visit to Afghanistan on Saturday. His plans to visit the country were kept secret for security reasons. At his first news conference as defense secretary, Panetta said efforts to defeat al Qaeda now centered on eliminating some 20 key leaders based in Pakistan, Yemen, Somalia and North Africa. \"I think now is the moment, following what happened with bin Laden, to put maximum pressure on them, because I do believe that if we continue this effort, that we can really cripple al Qaeda as a threat to this country,\" he said. \"We\'re within reach of strategically defeating al Qaeda.\" He also said Ayman al-Zawahri, who succeeded Bin Laden as Al Qaeda chief, is hiding in northwestern Pakistan\'s tribal belt. \"He\'s one of those we would like to see the Pakistanis target,\" he said. Al-Zawahiri, 59, a qualified surgeon, was former al-Qaeda chief Osama bin Laden\'s personal advisor and physician. He is on the CIA wanted list for allegedly planning terrorist attacks on U.S. embassies in Tanzania and Kenya in 1998 and has a $25 million bounty on his head.