ROBERT SIEGEL, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.
MICHELE NORRIS, host:
And I'm Michele Norris.
The leaders of Pakistan and Afghanistan sat down with President Obama today at the White House. Mr. Obama called the meetings extraordinarily productive. The talks are unfolding against a backdrop of concern about nuclear-armed Pakistan's stability. President Obama says he's confident that Pakistan's nuclear arsenal is secure. But as insurgents creep deeper into country, there are growing fears that those weapons could fall into the wrong hands.
NPR's Mary Louise Kelly reports.
MARY LOUISE KELLY: Pakistan guards the secrets of its nuclear program closely. U.S. intelligence officials believe Pakistan has somewhere between 60 and a hundred nuclear weapons. They're spread around the country and Pakistan is building more, says Zia Mian, a Princeton University physicist and expert on South Asia's nuclear programs.
Professor ZIA MIAN (Physicist, Princeton University): Pakistan has two more reactors for making weapons plutonium currently under construction. So there's a very large, determined effort to expand their capacity to make nuclear weapons material.
KELLY: U.S. officials say they've learned through covert sources where many of Pakistan's nuclear sites are located, but they don't know all of them. And that's deliberate on the part of the Pakistanis, says Michael Krepon of the Stimson Center in Washington.
Mr. MICHAEL KREPON (Co-Founder, Henry L. Stimson Center): Pakistan is pretty careful not to tell the United States everything the United States wants to know about these nuclear facilities. And that's because Pakistan doesn't completely trust the United States.
KELLY: Pakistan has long worried that the U.S. might try to destroy its arsenal. But in the wake of revelations about the nuclear black market run by Pakistani scientist A.Q. Khan, the U.S. has pushed for more access.
The Bush administration spent tens of millions of dollars to help secure Pakistan's weapons, a program that Admiral Mike Mullen, the chairman of the Joint Chiefs, alluded to at the Pentagon this week.
Admiral MIKE MULLEN (Chairman, Joint Chiefs of Staff): I know what we've done over the last three years specifically to both invest, assist, and I've watched them improve their security fairly dramatically over the last three years.
KELLY: The U.S. has paid for nuclear tracking devices, for security improvements at Pakistan's nuclear bunkers, and for improving background checks for workers at nuclear sites. But analysts say it's impossible to monitor whether Pakistan has implemented these improvements or whether, in a crisis, they would actually work.
Which brings us to the critical question: with turbulence spreading in Pakistan, how secure are the country's nuclear weapons? Admiral Mullen says everyone recognizes the worst-case scenario would be for terrorists to seize a bomb.
Adm. MULLEN: I don't think that's going to happen. I don't see that in any way imminent whatsoever at this particular point in time.
KELLY: This is the official U.S. government line. But privately, some officials say they're nervous. So is Matthew Bunn. He works on nuclear proliferation issues at Harvard's Kennedy School of Government.
Professor MATTHEW BUNN (John F. Kennedy School of Government, Harvard University): The thing that worries me most is theft of a actual nuclear weapon or the materials needed to make one.
KELLY: But aside from the weapons themselves, there's the pool of technical knowledge: the scientists, engineers and technicians who report to work every day at Pakistan's nuclear facilities. Pakistan has acknowledged that two of its nuclear scientists traveled to Afghanistan to meet with al-Qaida's leaders back in 2001.
Bunn says Pakistan does have effective security systems in place, but there's no question its nukes are at risk.
Prof. BUNN: The reality is it's impossible to judge, you know, what the percentage chance of something like this happening is. But it's not zero.
KELLY: And do you think it's getting bigger?
Prof. BUNN: I think it's getting bigger just because the threat is getting bigger. The terrorists' ability to operate throughout Pakistan is clearly increasing. Then the question is whether their ability to infiltrate Pakistani nuclear and security forces is also increasing.
KELLY: And that's still an open question, Bunn says. But he adds, given the potentially catastrophic consequences if Pakistan's nuclear weapons were to fall into the wrong hands, it's worth the U.S., quote, "spending a lot of time right now, making sure that doesn't happen."
Mary Louise Kelly, NPR News, Washington.
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