In a call to her Pakistani counterpart this month, secretary of state Hillary Clinton reiterated the Obama administration's counterterrorism "red line": The US reserved the right to attack anyone who it determined posed a direct threat to US national security.
Foreign minister Hina Rabbani Khar responded in kind, telling Clinton that Pakistan's red line was the violation of its sovereignty. Any unauthorised flight into its airspace, Khar bluntly told Clinton, risked being shot down.
The conversation, recounted by US officials, was one of the few high-level exchanges between the two governments in recent months, and it illustrated the depths to which US-Pakistan relations have fallen after a November border clash in which a US air assault killed 24 Pakistani soldiers.
The "fundamentals" of mutual interest in destroying al-Qaeda and safely managing Pakistan's nuclear arsenal haven't changed, said a senior administration US official, who, like several sources in this article, discussed sensitive diplomatic matters on the condition of anonymity. But the two countries are groping their way toward what he called "a new normal," somewhere between the strategic alliance that President Obama once proffered in exchange for Pakistan severing its ties with militants, and a more businesslike arrangement with few illusions.
In the United States, Obama is under political pressure to show Islamabad who is the global boss. Patience here has grown paper-thin with what is seen as Pakistani double-dealing and intransigence that is getting in the way of efforts to wind down the Afghan war.
In exclusive partnership with The Washington Post.