"I don't think that's going to happen," said Adm. Mike Mullen. "I don't see that in any way imminent whatsoever at this particular point in time."
But Adm. Mullen acknowledged there's a limit to what he knows since Pakistan guards its doomsday secrets as jealously as the U.S. guards its own, reports CBS News national security correspondent David Martin.
"Much of the complex is largely secret and kept so necessarily by the Pakistani government and so I'm not sure we know as much as we should," said CBS News consultant Juan Zarate.
Zarate worked with Pakistan on improving security at top secret plants during the Bush administration. He says the U.S. is not sure exactly how many weapons the Pakistanis have or where they all are.
"There are and have been Pakistani scientists or elements of the complex that have had sympathies and met with people who would be considered to be our enemies," Zarate said.
Shortly before 9/11 Osama bin Laden met directly with two Pakistani nuclear scientists. And former CIA officer Rolf Mowatt Larssen, who knows as much about Pakistan's nuclear complex as any American, says Taliban and al Qaeda sympathizers remain its Achilles heel.
"Security is strong," Larssen said, "particularly given the seriousness with which the Pakistani government approaches this unless there are people on the inside who are willing to work with terrorists."
The insiders might not be able to steal a full up weapon but might be able to smuggle out either the material or the know how to make one.
"Material that typically finds its way for sale by a terrorist group or another buyer comes from the production of nuclear materials and can be perhaps taken out of a facility," Larssen said.
You don't have to be a nuclear expert to know that in a country as unstable as Pakistan there are more chances for things to go wrong. In a country with nuclear weapons that means more chances for disaster.