The Obama administration has called off negotiations with Pakistan aimed at reopening supply routes for the war in Afghanistan, baring the depths to which US-Pakistan relations have plunged in recent months.

The Pentagon announced Monday that the US negotiating team that had been locked in discussions with Pakistani officials for months would leave the country without securing a deal. The announcement left some experts in US-Pakistan relations comparing the new low point in relations to 1989, when the US cut off aid to Pakistan over its unveiling of a clandestine nuclear weapons program.

“There are always peaks and valleys in any diplomatic relations, but in US-Pakistan relations it’s been almost all valleys for a good period of time now,” says Malou Innocent, a specialist in South Asian issues at the Cato Institute in Washington. “The question now is, how much lower can the valleys go?”

At the State Department, a spokeswoman, Victoria Nuland, said the US has no plans for resuming the talks, and suggested that a return to negotiations was now in Pakistan’s hands.

Pakistan closed its borders to truck convoys supplying US and NATO troops in Afghanistan last November, after US forces launched airstrikes against a Pakistani border outpost, killing two dozen border soldiers. A deal to reopen the border seemed near as NATO leaders met at a summit in Chicago in May, but talks remained snagged on two contentious points: Pakistan’s demand that the US offer a formal apology for the November border outpost attack, and Pakistan’s demand that the US pay considerably higher fees for each of the thousands of trucks carrying supplies into Afghanistan.

The United States refused to go beyond the “regret” President Obama expressed over the botched border attack, and it balked at the significantly higher truck fees Pakistan sought, with some officials calling the demand “blackmail.”

But even those issues probably could have been overcome by now if it weren’t for the broader context of steadily deteriorating relations, regional experts say.

Some officials were already speculating about a “divorce” in the troubled US-Pakistan relationship in 2011 after the furor over the case of a CIA operative who killed two Pakistanis who were following him. But then came the secret raid into Pakistani territory in May 2011 that resulted in the death of Osama bin Laden, and Pakistan’s demands for a halt in drone strikes and expulsion of US drones from a Pakistani air base.

More recently, NATO commanders have openly criticized Pakistan for harboring Taliban forces that cross over the border and target US and NATO troops, and Pakistan has found the Pakistani doctor who helped the US locate bin Laden guilty of treason, over US objections. And just last week, Defense Secretary Leon Panetta suggested to Indian officials that Pakistan is not exactly the most reliable US partner.

“Even with the killing of the two dozen border guards, I think it would have been possible to reach a deal on the border crossings, if it weren’t for the broader deterioration,” says Ms. Innocent. “The over-all crisis in the relationship won out, making it impossible to reach any kind of deal.”

The US decision to end talks without a deal could still be something of a strong-arm tactic, some analysts say, to get the Pakistanis to consider the substantial revenues they’d be giving up and to reconsider. Mr. Obama has pledged to withdraw all of the 33,000 “surge” troops he sent into Afghanistan by the end of the summer. But all US and NATO combat troops are not to be out until the end of 2014, allowing some time for a Pakistani border deal.

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In the meantime, most NATO supplies will be entering – and leaving – Afghanistan through the longer northern route through Russia, Central Asia, and Europe.

Cato’s Innocent notes that the prospect of completing the Afghanistan drawdown via the northern route will continue to be an incentive for the US to patch things up with Pakistan, for the simple reason that the northern route is at least three times costlier than going through Pakistan.