Pakistan’s precise military budget is not known, and while the American aid cutoff would probably have a small impact on the overall military budget, it would most directly affect the counterinsurgency campaign. The Pakistani Army spends nearly one-quarter of the nation’s annual expenditures, according to K. Alan Kronstadt of the Congressional Research Service.

While some senior administration officials have concluded that Pakistan will never be the kind of partner the administration hoped for when President Obama entered office, others emphasize that the United States cannot risk a full break in relations or a complete cutoff of aid akin to what happened in the 1990s, when Pakistan was caught developing nuclear weapons.

But many of the recent aid curtailments are clearly intended to force the Pakistani military to make a difficult choice between backing the country that finances much of its operations and equipment, or continuing to provide secret support for the Taliban and other militants fighting American soldiers in Afghanistan.

“We have to continue to emphasize with the Pakistanis that in the end it’s in their interest to be able to go after these targets as well,” Defense Secretary Leon E. Panetta told reporters on Friday en route to Afghanistan.

Some American officials say Pakistan has only itself to blame, citing the Pakistani military’s decision to distance itself from American assistance in response to the humiliation suffered from the American commando raid in Abbottabad, Pakistan, that killed Osama bin Laden, as well as rising anger from midlevel Pakistani officers and the Pakistani public that senior military leaders, including Gen. Ashfaq Parvez Kayani, the powerful army chief of staff, are too accommodating to the Americans.

Pakistan shut down the American program to help train Pakistani paramilitary troops fighting the Taliban and Al Qaeda in the lawless border regions near Afghanistan, prompting the Americans to take with them equipment Pakistani troops used. The Central Intelligence Agency has been relying more heavily on flying armed drones from Afghanistan since Pakistan threatened to close down a base the C.I.A. was using inside the country.

But in private briefings to senior Congressional staff members last month, Pentagon officials made clear that they were taking a tougher line toward Pakistan and reassessing whether it could still be an effective partner in fighting terrorists.