President Obama's national security adviser demanded Sunday that Pakistan let American investigators interview Osama bin Laden's three widows, adding new pressure in a relationship now fraught over how Bin Laden could have been hiding near Islamabad for years before he was killed by commandos last week.
Both the adviser, Thomas E. Donilon, and Mr. Obama, in separate taped interviews, were careful not to accuse the top leadership of Pakistan of knowledge of Bin Laden's whereabouts in Abbottabad, a military town 35 miles from the country's capital. They argued that the United States still regards Pakistan, a fragile nuclear-weapons state, as an essential partner in the American-led war on Islamic terrorism.
But in repeatedly describing the trove of data that a Navy Seal team seized after killing Bin Laden as large enough to fill a small college library, Mr. Donilon seemed to be warning the Pakistanis that the United States might soon have documentary evidence that could illuminate who, inside or outside their government, might have helped harbor Bin Laden, the leader of Al Qaeda, who had been the world’s most wanted terrorist.
The United States government is demanding to know whether, and to what extent, Pakistani government, intelligence or military officials were complicit in hiding Bin Laden. His widows could be critical to that line of inquiry because they might have information about the comings and goings of people who were aiding him.
"We have asked for access," Mr. Donilon said on the CNN program "State of the Union," "including three wives who they now have in custody from the compound, as well as additional materials that they took from the compound."
The request had echoes of previous struggles with Islamabad, starting with the days right after the September 11, 2001, terrorist attacks. Then, the United States insisted that Pakistan clearly choose sides and join the United States in fighting Al Qaeda, and Pakistan formally broke ties with the Taliban government, which was still in power in Afghanistan. But ever since, Washington has frequently lost out in its efforts to seek information about the loyalties and actions of top Pakistani officials.
Eight years ago, for example, the Bush administration demanded interviews with Abdul Qadeer Khan, the chief of Pakistan's main nuclear weapons laboratory, as the United States sought to understand who in the Pakistani military or intelligence apparatus had helped sell nuclear weapons technology and designs to Libya, North Korea and Iran. Pakistan has refused, perhaps because Mr. Khan, while seeking freedom from house arrest, briefly threatened to tell all.
As one American official said after Mr. Donilon spoke Sunday: "Our guess is that the wives knew just who was keeping Bin Laden alive for all these years." He added later, "It's the Khan case all over again." He insisted on anonymity as the United States tries to ease Pakistan's anger over Mr. Obama's decision to conduct the raid without telling Pakistani officials in advance, or seeking their involvement.
The Pakistani government has said nothing about allowing interviews of the wives, who were among the handful of survivors of the raid. One wife was shot in the leg by commandos as she tried to protect Bin Laden moments before he was killed.
Pakistan has said it will conduct its own investigation, but American officials doubt it will be credible. For more than two years Pakistan has slow-walked investigations into the 2008 siege in Mumbai, India, by a terrorist group, Lashkar-e-Taiba, that is believed to have strong links to portions of the Pakistani intelligence apparatus. To the distress of Pakistani officials, a trial scheduled to start soon in Chicago is expected to reveal evidence about the role in that attack of an officer of the Inter-Services Intelligence, Pakistan's main military intelligence agency.
The sparring over the investigation about Bin Laden's support structure threatens to go to the heart of what top American intelligence officials now routinely call the "double game" played by Pakistan. Mr. Obama alluded to that on "60 Minutes" on Sunday evening, saying, "We think that there had to be some sort of support network for Bin Laden inside of Pakistan."
Mr. Obama added: "But we don't know who or what that support network was. We don't know whether there might have been some people inside of government, people outside of government, and that's something that we have to investigate, and more importantly, the Pakistani government has to investigate."
The debate inside the administration over how hard to press Pakistan for answers — and whether to make public any evidence the United States possesses — has revived the question of whether it is time to dispense with, or radically amend, the unspoken bargain between Islamabad and Washington.
For years, the terms of that deal were simple: for the sake of getting Pakistani assistance in hunting down Qaeda leaders, Washington funneled billions of dollars to the Pakistani military. And it said next to nothing about its fears that fundamentalists were burrowed in Pakistan’s huge nuclear complex, or about the country's race to expand its arsenal, one of the fastest-growing in the world, a buildup that American officials fear could put more nuclear material at risk of falling into the hands of terrorists.
But as Mr. Donilon argued implicitly on Sunday, an alternative to that bargain could be even worse. Severing Pakistan's funds could end the cooperation on counterterrorism — which still works fairly well in some of the tribal areas — and it would mean losing virtually all visibility into the worrisome nuclear arsenal.
"We have had difficulty with Pakistan, as I said, but we've also had to work very closely with Pakistan in our counterterror efforts," Mr. Donilon said. "More terrorists and extremists have been captured or killed in Pakistan than in any place in the world."
As Leonard S. Spector, the director of the Washington office of the Monterey Institute's nonproliferation center, said, "It is hard to abandon Pakistan because of the danger of the nuclear program and the need for help in counterterrorism."
On Thursday, the Pakistani chief of staff, Gen. Ashfaq Parvez Kayani, threatened a rethinking of all intelligence and military cooperation with the United States if it ever again mounted an operation similar to the Bin Laden raid. (Mr. Donilon refused Sunday to rule out a repeat.)
But the military council, reacting to widespread fears in Pakistan that a similar American commando operation could seize Pakistan's arsenal of roughly 100 nuclear weapons, told Pakistani reporters that the country's weapons and materials were "well protected" and that "an elaborate defensive mechanism is in place," according to The Frontier Post, a Pakistani newspaper.