By Steven Mufson
Washington Post Staff Writer
Sunday, November 4, 2001; Page A27

About two weeks after the Sept. 11 terrorist attacks, a group of medium-level Bush administration officials met with experts on South Asia for a discussion of whether war in Afghanistan might detonate a series of bigger problems in Pakistan -- including the loss of control of Pakistan's nuclear arsenal.

That arsenal holds about 30 nuclear weapons and perhaps as many as 50, according to experts on Pakistan's nuclear program. There has been mounting concern in the United States that those weapons, their plans or some of the radioactive materials could fall into the hands of terrorists or their allies should the Pakistani government fall as a result of its decision to support the U.S.-led war in Afghanistan.

"If domestic instability leads to the downfall of the current Pakistani government, nuclear weapons and the means to make them could fall into the hands of a government hostile to the United States and its allies," said David Albright, a South Asia expert at the Institute for Science and International Security.

Those fears were fanned a week ago when Pakistan detained two retired nuclear scientists, including Sultan Bashiruddin Mahmood, the former chief designer and director of the country's Khoshab Atomic Reactor who for the past three years has run a relief organization and traveled frequently to Afghanistan.

Mahmood was a pioneer in Pakistan's efforts to enrich uranium, a key ingredient for nuclear weapons, and held a patent on a technique for stopping leaks of heavy water from enrichment plants. Later he helped manage the construction of a reactor that produces plutonium, also used in nuclear weapons.

Mahmood has made no secret of his political views. After Pakistan exploded a nuclear device in May 1998, Mahmood said the country should not give in to international pressure to sign the Comprehensive Test Ban Treaty. Instead, he said, Pakistan should enhance its capability to "at least match our enemy," India, "in order to safeguard our independence."

The other detained nuclear scientist, Abdul Jajid, worked in Pakistan's Atomic Energy Commission.

Pakistan has asserted that its nuclear arsenal is safe. Pakistani Foreign Minister Abdus Sattar said in a statement Friday that "Pakistan has an impeccable record of custodial safety and security free of any incident of theft or leakage of nuclear material, equipment or technology."

Though the United States usually supports civilian control of nuclear weapons around the world, it has endorsed continued military control of the weapons in Pakistan because the military is seen as more professional and stable than other elements of Pakistani society. Experts say the military chain of command appears intact despite turmoil and reshuffling at the top of the government, and most of the sympathizers of Afghanistan's ruling Taliban militia in the government are believed to be in the intelligence service.

But Bush officials remain anxious. John R. Bolton, undersecretary of state for arms control and international security, without singling out Pakistan, said Thursday that since Sept. 11 "my concern about nuclear weapons everywhere has gone up." He said he worried that a hostile state, or nonstate organization, might acquire such a weapon and that the attacks in New York showed they would be willing to use them.

Defense Secretary Donald H. Rumsfeld said Thursday that the United States had "certain knowledge" that the al Qaeda terrorist network headed by Saudi-born fugitive Osama bin Laden "had an appetite for acquiring weapons of mass destruction of various types, including nuclear materials."

A recent article in the New Yorker magazine by Seymour Hersh alleged that the U.S. military had a secret plan to destroy Pakistan's nuclear weapons, and that a special team had trained with Israeli advice and assistance. The State Department and Pentagon have denied the report.

Experts doubt such plans could succeed in any case. Because of Pakistan's long-standing fear that Israel, India or the United States might seek to destroy its nuclear weapons program, Pakistan's weapons are probably spread among several sites, making it difficult for any foreign special operations force to destroy or defuse. Experts say Pakistan might keep its warheads separate from missiles, for safer storage.

"People talk about getting the nuclear weapons. I don't know how you would do that," Albright said. "I think it would be very dangerous right now. The Pakistanis are very paranoid about what U.S. intentions are right now."

Administration officials are eager to increase the safety of Pakistan's nuclear arsenal. But they want to do so in a way that would not give Pakistan greater confidence to deploy the weapons or fan fears in Islamabad that the United States simply wants to collect information about the weapons so they could be destroyed.

Secretary of State Colin L. Powell said last week that he had discussed the issue with Pakistani President Pervez Musharraf during his visit to Islamabad last month. "He knows that if he needs any technical assistance on how to improve that security level, we'd be more than willing to help in any way that we can," Powell said.

Some administration officials have raised among themselves the possible transfer of "permissive action links," devices that would prevent warheads from being armed unless a number of people punched in codes. But many experts worry that such devices would encourage Pakistan to deploy weapons now kept in pieces for safekeeping.

Robert Einhorn, the Clinton administration's top nonproliferation official, said the United States should limit aid to improvements in the physical security around nuclear weapons sites through better surveillance equipment.

"We should pursue a program of cooperation that does not contribute to the operational capability of Pakistan's nuclear force," said Einhorn, a fellow at the Center of Strategic and International Studies.

That, however, might not help if the government falls. "The real threat is not that some guys with beards are going to run through and capture these things but that, with a change in government, control will change hands. That's not something better fences is going to solve," said George Perkovich, author of a book on Pakistan's nuclear weapons.

Most experts say the greatest terrorist danger comes from the possible theft of nuclear material, such as enriched uranium or plutonium. They said the theft of a nuclear weapon would be more difficult and more easily detected by Pakistani authorities.

That fissile material could be given to Iraq, which has sought to make its own nuclear weapons.

Gary Milhollin of the Wisconsin Project said an even greater danger would be that a terrorist could obtain nuclear waste from a Pakistani plant and use it in a conventional explosion to spread hazardous radioactive material. Though the explosion would kill more people, at least initially, than the radioactive waste, it would have a "terror effect," Milhollin said.