In the decade since September 11, 2001, ambiguity has been a cornerstone of US-Pakistani relations. The Americans, continually stung in Afghanistan by Pakistan-based militants, have as much as possible given Pakistani leaders the benefit of the doubt, saving the finger-wagging for behind closed doors.
Last week brought the strongest signal that the feud has gone public. Washington has a good argument that its "ally" is playing a double game, but a heavy-handed response will only make the situation worse.
On Thursday, the top US military officer, Admiral Mike Mullen, blamed Haqqani operatives "with ISI support" for a series of recent attacks in Kabul, including a particularly bloody one on the US embassy. For a military man who chooses his words carefully, calling Inter-Services Intelligence (the most influential of Pakistan's security services) a supporter of terrorism is as unambiguous as it comes.
It is not, however, a surprise to anyone. The Haqqani network, which straddles the Afghan-Pakistani border, is known to have had deep ties to intelligence agencies in Pakistan and Saudi Arabia (and even the US) during the 1980s. Since the 2001 US invasion, the network has become one of the most dangerous elements of the Taliban insurgency.
The question is what comes next. Daniel Markey, a Pakistan expert at the Council on Foreign Relations, told America's National Public Radio that Washington appears willing do what it must to wipe out fighters loyal to the Haqqanis. That could mean expanding special forces operations on sovereign Pakistani territory.
But that would be a shortsighted solution that would do more harm than good. The US drone assassinations in Pakistan have had a marked tactical impact, but the United States is not going to kill its way to victory. Few targets are high enough value to warrant anti-American sentiment and diplomatic rows. Sending US commandos into North or South Waziristan would only create more enemies, not to mention risk a bloodbath.
Washington needs to recognise its limits in being able to influence Islamabad. Pakistan is splintered along civil, military and intelligence lines; even the powerful army chief, General Ashfaq Kayani, is unable to exert full control.
But there is also no use pretending that all is right in the relationship. Threats to cut US funding have not influenced behaviour, but at the least aid should be reconsidered - apparently some of those funds are going to its enemies in the field. Diplomacy, not unilateral action, is still the answer.