CIA spokesman declined to comment.
Pakistan's sovereignty has been an issue in the presidential campaign. Sen. Barack Obama, the presumptive Democratic nominee, said at one point that he would unleash strikes into Pakistan without Islamabad's approval to hit bin Laden and other al Qaeda leaders.
The U.S. has options for sending special operations teams into Pakistan if bin Laden's exact location is determined, but military officials said it would be the Predator, not boots on the ground, that would be dispatched to kill the al Qaeda leader.
This is because a Predator could be airborne - or redirected in flight - in a matter of minutes. In contrast, special operations forces in Afghanistan would have to be assembled, briefed on the mission and then dispatched by helicopter - a time-consuming and risky process.
By not requesting Pakistan's approval first, the U.S. would avoid the risk of breaching operational security. Washington still harbors suspicions about Pakistan's Inter-Service Intelligence agency (ISI), which helped establish pro-al Qaeda Taliban rule in Afghanistan.
It is one thing to have Pakistan's permission to shoot bin Laden on sight. It is another to find him.
"It's a needle in a haystack," said one intelligence official.
For nearly seven years, since his escape from Afghanistan's Tora Bora mountain region, bin Laden has evaded capture.
The reasons given by intelligence officials: He stopped communicating on radios and telephones to avoid being intercepted by the National Security Agency; he is protected by militant leaders whose tribes have been infiltrated by al Qaeda operatives who impose a no-talk discipline; the CIA has been unable to penetrate this tribal ring of security to find a spy who might disclose his location; and bin Laden moves frequently amid the FATA's vast, rugged terrain.
'NEEDLE IN A HAYSTACK': Osama bin Laden has evaded capture for nearly seven years.
"I would say to you in the last seven years there has been a lot of success in terms of finding that second- and third-level al Qaeda guy," Mrs. Perino said. "And we have been able to prevent attacks so far. But one of the things that we're up against is that we have a very determined enemy. They hide in caves, they respect no uniform, they are in a very treacherous geographic area that's very hard to get into."
The NSA installed a network of electronic boxes in the Afghan mountains to absorb communications from the FATA. The chatter has helped the CIA identify militant hide-outs and training bases, but the network has not picked up bin Laden's voice.
The military's chief terrorist hunting unit is Joint Special Operations Command (JSOC), a mix of Army Delta Force, Navy SEALs and a special intelligence unit known as Task Force Orange.
An intelligence source said most JSOC assets are committed to Iraq to hunt a list of high-value targets within the al Qaeda in Iraq organization. At one point last year, the JSOC contingent in Afghanistan was down to just 30 SEALs.
The U.S. Special Operations Command, which oversees the JSOC, does not discuss the unitīs numbers.
