THE fraught relations between Pakistan and the US have often been likened to a bad marriage in which the two partners can't live with each other, but are bound together by mutual dependency.

I knew a few similar relationships, and it was painful to watch two people tearing each other apart. I was in the US when the two Pakistani border posts along the Afghan border came under fire from Nato helicopter gunships, killing 24 soldiers. When questioned about the angry Pakistani response, I asked my American friends what their reaction would have been had Pakistani fire inflicted such heavy casualties on American troops in Afghanistan.

The truth is that all hell would have broken loose, with loud calls from across the American spectrum demanding immediate retaliation. Pakistani offers to mount a full investigation would have been brushed aside as a whitewash. Politicians would have called for a suspension in military aid — the biggest stick the Americans have in their relationship with Pakistan.

In the event, Pakistan has used all the sticks in its cupboard: a halt in Nato supplies, notice to vacate Shamsi airbase in Balochistan and the decision to refuse to attend the Afghan security conference in Bonn next week. All these actions underline the transactional nature of the Pakistan-US relationship: if you give us this, we will give you that. And as a rentier state, Pakistan had some valuable geopolitical real estate to offer.

The reality is that there has never been a convergence of values or long-term interests between the two countries, despite their long and troubled alliance. True, both states started off by entering into anti-communist pacts in the 1950s. But for Pakistan, this was a way of acquiring American arms in its rivalry with India.

Once the USSR imploded, the rental value of Pakistan fell to zero in US eyes. Military and economic sanctions to discourage nuclear proliferation kicked in, the supply of F-16 fighter planes we had paid for was blocked and Pakistan was declared an international pariah when we tested our nuclear devices in 1998.

Just as it seemed the relationship was doomed forever, Osama bin Laden launched his war on America, and with 9/11, a second honeymoon began. But the lack of any solid basis to the partnership beyond short-term needs has meant that it is always going to be hostage to outbursts and spats that threaten to spiral out of control.

Ultimately, the relationship is resurrected each time it hits rock bottom because of our mutual need for each other. Our military desperately needs the high-tech weaponry it is unable to procure elsewhere and our economy can't do without the assistance that trickles in fitfully from Washington. More urgently, we need American support for our frequent loan requests for multilateral aid.

American needs are more straightforward: Pakistan's approval for the use of its airspace to support Nato troops in Afghanistan from aircraft carriers in the Arabian Sea, the use of our road network to carry supplies overland and the interdiction of cross-border militancy.

It is this last task that has proved so contentious. Over the years, as Nato casualties have mounted, western leaders have blamed Pakistan for 'not doing enough' to combat militants based on its soil, and for not stopping them from crossing into Afghanistan at will to fight Nato and Afghan forces.

This is a question that frequently came up during the talks and media interviews I gave in America recently on my book tour. I tried to explain Pakistan's red lines to my largely American audiences. Our defence establishment's misplaced preoccupation with the threat it perceives from India is obviously one.

Another is the army's need to have proxies in place for the post-US scenario in Afghanistan in which the pre-9/11 civil war is likely to resume. The third lies in the dangers inherent in taking on the Haqqani network at a time when the army has its hands full already, fighting the local Taliban. And finally, there are problems inherent in repeatedly ordering our Frontier Corps to fire on fellow Pakhtuns and fellow Muslims.

I also reminded my listeners of the anger caused by the charge that the Pakistan Army was not doing what it was supposed to despite the billions it was getting from the Pentagon. Our officer corps is furious at being thought of as a mercenary army, doing the bidding of foreigners for financial considerations. In its eyes, it has national interests to protect, irrespective of the military aid it is getting.

Clearly, there is a mismatch of expectations here. For the American public, politicians and media, the narrative is about paying hard cash to buy certain services, and getting short-changed. This is the nature of a transactional relationship: when the customer doesn't think he's getting what he paid for, he complains loud and hard.

From the popular Pakistani perspective, we have already paid too high a price for entering into this war on America's side. In terms of lives lost as well as economic damage, the public perception — whipped up by the populist media — is that enough is enough.

According to an opinion poll published by this newspaper, 55 per cent of all Americans consider Pakistan to be an enemy. This bleak view of its alliance partner is similar to the perception of two-thirds of all Pakistanis about the US. So clearly, there is not much warmth in the doomed marriage.

Nevertheless, the joyless couple are condemned to carry on with a façade of a united front for the next three years when US forces are scheduled to begin pulling out of the quagmire Afghanistan has proved for them. This time, though, there is little prospect of the couple getting back together.

From the American perspective, a combination of a slumping economy and 15 years of bad vibes will make any resumption of aid politically impossible. As it is, there is increasing resistance to military and economic assistance. Only the presence of US troops in the region is making it possible for the Obama administration to continue disbursing aid.

For many Pakistanis, this cut-off will only reinforce the popular image of America — fed by years of propaganda — as a fickle, fair-weather ally who abandons us when we aren't needed.

The writer is the author of Fatal Faultlines: Pakistan, Islam and the West .

irfan.husain@gmail.com