WASHINGTON - Since 2001 the United States has tried virtually every strategy available to persuade Pakistan's army to take the threat of militancy more seriously, but 12 years and $28 billion in aid later, all the American approaches are widely viewed as having failed.
First, the Bush administration heaped praise on former Pakistani President Pervez Musharraf, agreed to reimburse the Pakistani army for anti-Taliban military operations and launched drone strikes that killed al Qaeda leaders and militants wanted by the Pakistani government.
Adopting a more confrontational stance, the Obama administration unilaterally carried out the raid that killed Osama bin Laden, vastly increased aid to Pakistan's weak civilian institutions and, at times, cut off aid to the Pakistani military.
Yet the militants continue to operate, ever more brazenly, as illustrated by Tuesday's harrowing attack on a school in Peshawar, in which 132 students were killed by a faction of the Pakistan Taliban. And with the United States increasingly focused on other crises, Washington's options for bringing about change in an increasingly unstable Pakistan are dwindling fast.
"There is great 'Pakistan fatigue' in Washington," said Cameron Munter, who served as the American ambassador to Pakistan from 2010 to 2012. "Not only have the last dozen years been very difficult, but other challenges - from Syria to Ukraine to Iran, to name a few - demand our attention."
Although Tuesday's attack sparked widespread condemnation, current and former US officials expressed cynicism that the bloodshed would cause Pakistan's military to change its view of militants.
Munter and other officials said the United States has been unable to break a powerful, army-backed narrative in Pakistan that militant attacks are the result of America's war on terror. Foreign powers, not Pakistan, are responsible for growing militancy in Pakistan, according to the narrative. And Pakistan is not responsible for the problem and unable to stop it.
That narrative played out immediately when Pakistan's army chief, General Raheel Sharif, flew to Afghanistan within 24 hours of the attack to meet Afghan leaders. They said they had information that the school attack was directed by militants hiding inside Afghanistan.
"We are hoping that we will see strong action from the Afghan side in the coming days," said Pakistani army spokesman Major General Asim Saleem Bajwa.
One senior American official said he hoped the trip was not "communications Kabuki" designed to divert blame for the failure to stop the attack away from the Pakistani army. Analysts said the army is failing to live up to its decades-long history of training, funding and sheltering some militant groups and using them as proxies to counter archrival India in Afghanistan and Kashmir.
Since 2001 a parade of American officials - from presidents to CIA directors - have repeatedly warned Pakistan's generals that they will lose control of their militant proxies and eventually be attacked by them. Pakistani military officials have denied sheltering militants.
But some current and former US officials said the sheer brutality of this week's attack would intensify demands from Pakistan's public for the army to confront militancy. James Dobbins, who served as the Obama Administration's Special Representative to Afghanistan and Pakistan from 2013 to 2014, said there was also growing pressure from Pakistan's longtime ally China.
"I think they are pressing Pakistan to take this threat more seriously," he said.
Munter, the former ambassador, argued that the problem reflects a more fundamental question of whether militants have become so entrenched that the Pakistani army cannot defeat them.
The senior administration official was more optimistic, contending that even before the school attack, the Pakistani public was raising pressure on the army to act. The ongoing military operation in North Waziristan that militants said prompted the school attack was evidence of change.
"There has been a growing sense in Pakistan that this is an issue that they need to deal with," said the senior official, who asked not to be identified by name.
But Shamila Chaudhary, who served as senior director for Pakistan and Afghanistan on the National Security Council from 2010 to 2011, warned that as US attention has shifted elsewhere, the steady deterioration of Pakistan's institutions, security forces and economy has continued.
For years, Chaudhary said, she dismissed alarmist warnings from other US experts on Pakistan that the country's nuclear arsenal was unsafe. The inability of Pakistan's security forces to protect a military-run school, she said, has given her doubts regarding Pakistan's atomic arsenal for the first time.
"I will have a hard time saying to people that militants can never steal Pakistan's nuclear weapons," she said. "The more these things happen, that rate of risk goes ahead, and I just think, well, it could happen one day."