Ever since 9/11, the nightmare scenario for American security has been the possibility that terrorists could obtain nuclear weapons.
I've just come back from the place where, in theory, that might happen: Pakistan, a country that is thought to have about 50 nuclear warheads, where al-Qaida, the Taliban and other jihadis have established a substantial foothold.
The assassination of former Prime Minister Benazir Bhutto and the continuing instability in her country force us to ask a terrifying question: Could Pakistan's Islamic extremists seize a nuke or steal the fissile material for a dirty bomb?
Back in November, U.S. intelligence agencies assessed that Pakistan's nuclear arsenal was safe. The situation has deteriorated sharply since then. Are those weapons safe?
To search for answers, I visited a top security official responsible for the safety of Pakistan's nuclear program, two days after the death of Ms. Bhutto.
The official, a military general, declined to be identified because of the sensitive nature of his job. For two hours, using a slide presentation, he outlined a multilayered system of safeguards for weapons and materiel, along with an elaborate system of personnel checks for scientists and workers, designed to weed out any militancy or connection with terrorist elements.
The Nuclear Command Authority, made up of the president and prime minister, along with senior Cabinet members and military officials, controls the nukes and would decide on any deployment. The Personnel Reliability Program focuses on the most sensitive employees of the system, even after they leave it, including background checks and psychological testing. "There is no way a group of terrorists could penetrate our strategic facilities," said the security official.
The system was set up in 1999, after Pakistan's first detonation of a nuclear weapon in 1998; it was tightened after the nuclear scandal perpetrated by the father of the Pakistani bomb, Abdul Qadeer Khan, who sold nuclear weapons designs and components to Iran, North Korea and Libya in the 1980s and 1990s. Many experts believe senior Pakistani military and intelligence officials were complicit.
In today's uncertain Pakistani political climate, could another scientist provide nuclear material to Islamists? Could Islamist sympathizers within the military evade the scrutiny of the security system? The security official insisted that there would never be a repetition of the Khan.
Could there be a repetition, I asked, of the August 2001 meeting in Afghanistan at which two retired Pakistani nuclear scientists offered to help Osama bin Laden? "Today, that would not happen," the security official told me.
The professional qualifications of the top security official were impressive. The system he described was complex and substantial. Counterintelligence on weapons security now comes directly to the top security official, not routed via other intelligence agencies, some of which have had past connections with jihadis.
OK, I said, let's suppose the Pakistani security system works. But in a time of political uncertainty, could someone with Islamist sympathies take over the entire system? "The Taliban or al-Qaida are in no position to take over the central government and thereby the National Command Authority," came back the swift answer. This is probably true.
The problem is that Pakistan is entering uncharted political waters. Under President Pervez Musharraf, the military has been ambivalent about taking on Pakistani militants and has become demoralized by losses sustained in jihadi attacks. No political leader except Ms. Bhutto has spelled out clearly that this is now Pakistan's war, not a proxy war for American interests.
The greatest fear of U.S. experts on Pakistan's nuclear security is that disgruntled insiders could penetrate the security system. I want to believe that the Pakistani security system can weed out bad actors before they get their hands on fissile material. But can we be sure?
Trudy Rubin is a columnist for The Philadelphia Inquirer. Her column appears Tuesdays in The Sun. Her e-mail is firstname.lastname@example.org.