The Taliban's recent advances in Pakistan are intensifying concern about whether its nuclear arsenal is safe from terrorists.
Pakistan's president says it is. Asif Ali Zardari, who meets President Barack Obama in Washington on Wednesday, recently proclaimed that "the nuclear capability of Pakistan is under safe hands."
Available information suggests that Pakistan's secret nuclear sites are protected by crack troops and multiple physical barriers, making the risk from an outright Taliban attack relatively low.
A more worrying prospect for some experts is possible infiltration by radical Islamists of Pakistan's nuclear facilities.
Stringent security checks on personnel are meant to prevent that as well. But Pakistan's nuclear establishment has seen serious leaks of nuclear knowledge and materials by insiders in the past.
Top government scientist A.Q. Khan operated a global black market nuclear network for more than a decade until he was uncloaked by U.S. intelligence. And the CIA has confirmed a meeting between Khan associates and Osama bin Laden before the Sept 11, 2001 terror attacks.
The bin Laden factor
The issue of Pakistan's nuclear security is expected to come up during general discussions between Zardari and Obama on the Taliban insurgency.
Elements of the Taliban are associated with al-Qaida and are thought to have sheltered bin Laden for years in the rugged Pakistani border region to Afghanistan. The U.S. invasion of Afghanistan itself came after Taliban leader Mullah Omar refused to turn over bin Laden.
Bin Laden, in turn, has repeatedly expressed al-Qaida's desire to acquire the bomb.
When asked in 1998 if he had nuclear or chemical arms, he responded: "Acquiring weapons for the defense of Muslims is a religious duty. If I have indeed acquired these weapons, then I thank God for enabling me to do so."
Such aspirations have drawn not only U.S. concern.
Former Pakistani Prime Minister Benazir Bhutto warned before her 2007 assassination that al-Qaida affiliates could hijack Pakistan's nuclear weapons if the country fails to neutralize the Taliban. And International Atomic Energy Agency head Mohamed ElBaradei repeatedly invokes the threat of the bomb in terrorist hands as the greatest global threat to nuclear security.
Concerns thus persist, despite Pakistani assurances.
"We want to respect their sovereignty," said Obama recently. "But we also recognize that we have huge strategic interests, huge national security interests in making sure that Pakistan is stable and that you don't end up having a nuclear-armed militant state."
Multilayered security systems are in place to prevent nuclear mayhem, according to information leaked or publicly shared by Pakistani officials.
Pakistan's 60 plus warheads are believed to be stored separately from their delivery systems, with the nuclear cores removed from their detonators. The weapons are dispersed in as many as six separate locations, most of the south of the capital. And Pakistani officials say the weapons are fitted with code locks, with at least two people required to authenticate the codes before they can be released from storage.
Additionally specially trained troops patrol the inner perimeter of nuclear weapons depots and related locations, with some declared no-fly zones. Electronic sensors and monitoring devices are mounted at outer perimeters. And personnel assigned to sensitive nuclear positions go through regular background checks conducted by Pakistan's intelligence services.
People in charge
In Washington Monday, Adm. Mike Mullen, chairman of the U.S. Joint Chief of Staff, told reporters that — while he is gravely concerned about Taliban advances in Pakistan and Afghanistan — "I've watched them improve their (nuclear) security fairly dramatically over the last three years."
That includes trying to make sure those in positions of responsibility are reliable. William H. Tobey, the former deputy administrator for the U.S. National Nuclear Security Administration's Office of Defense Nuclear Nonproliferation, described Pakistani officials in charge of the country's nuclear weapons as "educated and professional."
"The government of Pakistan values its nuclear arsenal for strategic reasons, which means that they are highly motivated to protect it," he said.
Still, with anti-U.S. feeling running high in Pakistan, there is concern about insider sympathies for Islamic causes.
Iran, Libya and North Korea bought their weapons-capable know-how from Khan, a national hero for his pivotal role in developing the bomb for Pakistan who is lionized by Islamists for making it the world's only Muslim nuclear power. And the CIA is aware of two retired physicists from the Pakistan Atomic Energy Commission — Chaudiri Abdul Majeed and Sultan Bashiruddin Mahmood — meeting bin Laden shortly before the Sept. 11 attacks to offer him nuclear arms.
The relative isolation of the Pakistani military from the West is also a potential source of concern.
'Highly disciplined' military
The U.S. and other Western powers stopped training Pakistani officers after Islamabad secretly developed and then tested its nuclear bomb in 1998. While some ties have been resumed in recent years, the hiatus fed anti-U.S. sentiment among some officers now in senior positions.
"The Pakistan military is a serious military ... they are highly disciplined," says Robert Grenier, a former CIA station chief in Islamabad and now chairman for global security consulting with Kroll risk consultants in Washington. Still, he speaks of the danger that some within the military might "harbor a certain level of sympathy for the goals, if not the methods of the militants."
Also of concern are changing Taliban aspirations.
Pakistan's Taliban are an offshoot of Islamic tribal groups on the border with Afghanistan whose initial aspirations — autonomy from Islamabad to pursue their isolationist way of life — have mutated as they have mingled with more radical Afghan Taliban.
"The Taliban today are a different kind of radical," says Hassan Abbas, a former police chief of a region near the border tribal areas, and — like Tobey — now with Harvard's Belfer Center for Science and International Affairs. "They want to expand, they want to impose their view of their own religious dogma. They want to expand it to all of Pakistan."
George Jahn has covered the International Atomic Energy Agency and related nuclear strategic and tactical issues since 2002.