Advisers to U.S. President Barack Obama's administration say their worst security nightmare is the possibility that Pakistan -- a nuclear-armed country -- might fall under the control of Al-Qaeda militants.
Pakistani Prime Minister Yousuf Raza Gilani insists that no group will be allowed to challenge the authority of the government. Pakistani officials also insist that the country's nuclear arsenal is secure.
But U.S. officials including Secretary of State Hillary Clinton this week highlighted concerns about the security situation in Pakistan. Clinton described advances by Islamic militants in Pakistan as a "mortal threat" to the security and safety of the world.
George Perkovich, director of the Nonproliferation Program at the Carnegie Endowment for International Peace, says he has never been more concerned about the possibility of Pakistan's nuclear weapons falling into the hands of Islamist extremists.
"I would say that I thought [the threat] was exaggerated -- that there were 10 or 12 other [threats] in Pakistan that were more probable and were also very grave -- [but] it's gotten much worse in the last few years, and you have a sense of parts of Pakistan now becoming ungovernable by the Pakistani state," Perkovich says. "Today I'm feeling like we really, really have to focus on the nuclear danger in a way that I wouldn't have said was the case until recently. It's not an exaggeration to say that there is a risk."
Locked Up Tight?
Most experts say they have no doubt that Pakistan's nuclear arsenal is now under tight control by Pakistan's Strategic Plan Division -- the security structure headed by 58-year-old General Khalid Kidwai and intended to keep the weapons from falling into the hands of Islamic militants, Al-Qaeda scientists, or Indian saboteurs.
Jeff Lightfoot, assistant director of the Atlantic Council's program on international security, says he is not so worried about militants obtaining Pakistan's nuclear weapons under the army's current system of safeguards.
Lightfoot tells RFE/RL that he sees the recent extremist advances as a danger primarily to Pakistan itself -- and by extension, the wider region with Afghanistan and India.
He describes "the greatest threat" as a "gradual bleeding of Pakistani authority" that would leave large parts of the country outside central government control.
Lightfoot calls the military the "glue of the country" but questions its ability to demonstrate that it can control and defend Pakistan's borders and ensure sovereignty, something he labels "an ideology problem."
"In terms of the nuclear weapons and them falling into the hands of terrorists, the army may not necessarily be able to control all of Pakistan," Lightfoot adds, "but I don't think that necessarily translates into a breakdown of their nuclear-weapons command-and-control system."
Perkovich says current safeguards should ensure that any possible collapse of the civilian government in Islamabad would not affect the security of Pakistan's nuclear weapons -- at least, he says, as long as General Kidwai remains in control.
"The civil government is not relevant to the control of nuclear weapons in Pakistan; it is entirely an army issue," Perkovich says. "We do have a strong sense that [Pakistan's nuclear weapons] are controlled by elements in the army that have been selected and are reliable. As long as that control by this current military leadership remains strong, then I think one can have pretty good confidence that these weapons won't be used crazily."
But Perkovich says his concern centers around what could happen if pro-Islamist elements within Pakistan's military and security forces turned against Kidwai.
"The risk on the nuclear side is that the country falls apart or has a civil war that the bad guys win," Perkovich says. "The fear comes if there is a coup within the military so that, somehow, the people now in charge within the military get dispossessed of their nuclear weapons by other people in the military who would be less responsible."
To that "first fear," however, Perkovich adds another alarming scenario: "The second fear is [if] there is basically just a takeover by the Taliban and somehow the military crumbles and flees."
The size of Pakistan's nuclear arsenal is classified information in Islamabad. Pakistan has not signed the Nuclear Non-Proliferation Treaty and has been careful not to disclose the exact number or locations of its nuclear weapons. Estimates by experts and researchers range from around 50 nuclear weapons to as many as 150.
Former President General Pervez Musharraf declared in 2007 that the weapons were in a "disassembled state" -- most likely meaning that the warheads were kept separately from the ballistic missiles capable of delivering them to targets as far away as New Delhi, India.
General Kidwai has said that the nuclear warheads could be assembled very quickly with land- and air-delivery systems.
Seth Jones, a political scientist who is currently in Pakistan doing research for the RAND Corporation, tells RFE/RL that Pakistan has "dozens" of nuclear weapons dispersed in or near major cities throughout the country. He says that his recent visits to nuclear facilities in Pakistan suggest the country's weapons are still in a disassembled state.
"I've visited a number of the nuclear facilities [in Pakistan] and I'm fairly confident that security procedures are actually pretty good," Jones says. "The ones I've visited have included sites that hold fissile material and also that hold ballistic-missile technology -- where one could put nuclear weapons on and [that] would give Pakistan a range to target countries like India if there was an exchange."
He likens those facilities to "what one might see in China or, frankly, in the United States."
With his firsthand views of security for Pakistan's nuclear arsenal, Jones says he is most concerned about how a destabilized government in Pakistan might promote the spread of nuclear-weapons technology out of the country or to Al-Qaeda militants.
"In most of these scenarios, still, the likelihood that nuclear weapons are going to be used or come in the hands of militants or terrorists is highly unlikely," Jones says.
But he is quick to add that "where one might get concerned...is elements of the A.Q. Khan network that were involved in building Pakistan's atomic capability -- a range of scientists that have proliferated nuclear material to North Korea, Iran, and several other places."
In that respect, he cites a lesson that was learned under previous leadership in Islamabad, before the international community was fretting publicly about any "existential threat" to the Pakistani state posed by extremists.
"We know in the past that there have been talks between members of the A.Q. Khan network and militants, including Al-Qaeda several years ago," Jones says. "So is it possible that some technology at some point falls into the hands of terrorists? I think that's a more likely scenario than actual nuclear weapons coming out of [the Pakistan army's] control."