The relationship between the United States and Pakistan has long been one of grudging interdependency. The US needs Pakistan to help in the fight against the militants and to serve as a supply transit route for military operations in Afghanistan. Pakistan needs the US for financial aid, and access to international lenders and the global economy. But neither side much likes nor trusts the other. The relationship has always lurched from one crisis to another, but lately it has worsened and become toxic. Now senior officials from each side are publicly airing their anger and frustration with the other including outgoing CIA chief Leon Panetta, who has been nominated to be the next secretary of defence. This is a difficult challenge. The relationship with Pakistan is at the same time one of the most critical and yet one of the most complicated and frustrating relationships that we have, he told members of the Senate Armed Services Committee during his confirmation hearing. Compounding Problems In such a troubled relationship, its difficult to say definitively when things started to take a turn for the worse. Daniel Markey, a senior fellow for India, Pakistan and South Asia at the Council on Foreign Relations, says ties have been sorely strained for more than a year over the US buildup in neighbouring Afghanistan. But he says things really took a nosedive in January when Raymond Davis, a CIA security contractor, shot and killed two Pakistanis. Davis was arrested and detained for several months. During that time, it became quite clear that the United States was conducting covert operations against Pakistan. So that brought the rift out ... more into the open, Markey says. Markey says that rift was compounded by the May 2 attack that killed Osama bin Laden. The United States did not tell Pakistan about plans for Navy SEALs to raid bin Ladens compound. Meanwhile, Pakistan has expelled most of the roughly 135 American military trainers who were helping paramilitary forces with their counterinsurgency skills. Conflicting Priorities Shuja Nawaz, director of the South Asia Centre at the Atlantic Council, says Pakistanis never liked the idea of American soldiers in their country. He says the furore over the bin Laden raid gave the Pakistanis an opportunity to put an end to this relationship. Now clearly, it may not be entirely in their favour to give up the training support, but politically I think the military wanted to send a signal not only to the United States but to people inside Pakistan that it was taking a particularly tough position against the United States, Nawaz says. Pakistan also arrested several people who had given the CIA information about the bin Laden compound. The fact that Pakistan arrested those who helped the United States with the raid illustrates the conflicting priorities of the two countries. Markey of the Council on Foreign Relations says this has upset many members of the administration and Congress. They are baffled by it, theyre frustrated by it and theyre, many of them, quite angry. The only thing that has kept them from taking more immediate action is that when they ask the question, 'Well, what would be better than this? or 'How do we solve it? theres no clear answer, Markey says. Nawaz says the struggle for answers wont get any easier. He says just by coincidence, many of the leading Pakistan experts in the Obama administration are leaving office in the next few months. In the White House, at the National Security Council ... at the Department of Defence ... and then the top two people in the Office of the Defence Representative in Pakistan, who have developed enormously good personal relationships inside Pakistan, he says. So there is a wholesale movement of the Pakistan expertise out, and there is apparently not enough expertise in the pipeline. Nawaz says given that, hes uncertain what, if anything, can stop the downward trajectory in the US-Pakistan relationship. NPR