Potential vulnerabilities in Pakistan’s nuclear infrastructure have become a growing sore point between Washington and Islamabad. Pakistani soldiers monitor the Afghan border.

As the insurgency grows in Pakistan, concerns mount over the security of the country’s nuclear arsenal.


By DAVID E. SANGER - WASHINGTON


AS THE INSURGENCY of the Taliban and Al Qaeda spreads in Pakistan, senior American officials say they are increasingly concerned about new vulnerabilities for Pakistan’s nuclear arsenal, including the potential for militants to snatch a weapon in transport or to insert sympathizers into laboratories or fuel-production facilities.

The officials emphasized that there was no reason to believe that the arsenal, most of which is south of the capital, Islamabad, faced an imminent threat. President Barack Obama said recently that he remained confident that keeping the country’s nuclear infrastructure secure was the top priority of Pakistan’s armed forces.

But the United States does not know where all of Pakistan’s nuclear sites are located, and its concerns have intensified recently since the Taliban entered Buner, a district about 100 kilometers from the capital. The spread of the insurgency has left American officials less willing to accept assurances from Pakistan that the weapons are safe.

Pakistani officials have continued to avoid American requests for more details about the location and security of the country’s nuclear sites, the officials said.

Some of the Pakistani reluctance, they said, stemmed from longstanding concern that the United States might be tempted to seize or destroy Pakistan’s arsenal if the insurgency appeared about to engulf areas near Pakistan’s nuclear sites. But they said the most senior American and Pakistani officials had not yet engaged on the issue, a situation that may have changed during President Asif Ali Zardari’s visit last week with Mr. Obama in Washington.

“We are largely relying on assurances, the same assurances we have been hearing for years,”said one senior official who was involved in the dialogue with Pakistan during the Bush years, and remains involved today.“The worse things get, the more strongly they hew to the line,‘Don’t worry, we’ve got it under control.’”

In public, the administration has only hinted at those concerns, repeating the formulation that the Bush administration used: that it has faith in the Pakistani Army.

“I’m confident that we can make sure that Pakistan’s nuclear arsenal is secure,”Mr. Obama said April 29,“primarily, initially, because the Pakistani Army, I think, recognizes the hazards of those weapons falling into the wrong hands.”He added:“We’ve got strong military-to-military consultation and cooperation.”

But that cooperation, according to officials who would not speak for attribution because of the sensitivity surrounding the exchanges between Washington and Islamabad, has been sharply limited when the subject has turned to the vulnerabilities in the Pakistani nuclear infrastructure. The Obama administration inherited from President Bush a multiyear, $100 million secret American program to help Pakistan build stronger physical protections around some of those facilities, and to train Pakistanis in nuclear security.

But much of that effort has now petered out, and American officials have never been permitted to see how much of the money was spent, the facilities where the weapons are kept or even a tally of how many Pakistan has produced.

The facility Pakistan was supposed to build to conduct its own training exercises is running years behind schedule.

Mr. Zardari heads the country’s National Command Authority, the mix of political, military and intelligence leaders responsible for its arsenal of 60 to 100 nuclear weapons. But in reality, his command and control over the weapons are considered tenuous at best; that power lies primarily in the hands of the army chief of staff, General Ashfaq Parvez Kayani, the former director of Inter-Services Intelligence, the country’s intelligence agency.

For years the Pakistanis have waved away the recurring American concerns, with the head of nuclear security for the country, General Khalid Kidwai, dismissing them as“overblown rhetoric.”

Americans who are experts on the Pakistani system worry about what they do not know.“For years I was concerned about the weapons materials in Pakistan, the materials in the laboratories,”said Rolf Mowatt-Larssen, who ran the Energy Department’s intelligence unit until January, and before that was a senior C.I.A. officer sent to Pakistan to determine whether nuclear technology had been passed to Osama bin Laden.

“I’m still worried about that, but with what we’re seeing, I’m growing more concerned about something going missing in transport,” said Mr. Mowatt-Larssen, who is now at Harvard’s Kennedy School of Government in Cambridge, Massachusetts. Several current officials said that they were worried that insurgents could try to provoke an incident that would prompt Pakistan to move the weapons, and perhaps use an insider with knowledge of the transportation schedule to tip them off.

The Pakistanis, not surprisingly, dismiss those fears as American and Indian paranoia, intended to dissuade them from nuclear modernization. But the government’s credibility is still hurt by the fact that it used equal vehemence to denounce as fabrications the reports that Abdul Qadeer Khan, one of the architects of Pakistan’s race for the nuclear bomb, had sold nuclear technology on the black market.

In the end, those reports turned out to be true.