ISLAMABAD: Pakistan's civilian government should “bite the bullet” and re-open supply routes to Nato forces in Afghanistan in order to ease tensions with the United States, a senior US government official said on Tuesday.

The United States said on Monday it was withdrawing its team of negotiators from Pakistan without securing a long-sought deal on supply routes for the war in neighbouring Afghanistan, publicly exposing a diplomatic stalemate and deeply strained relations that appear at risk of deteriorating further.

“If the civilian government in Islamabad would bite the bullet and make the political decision to open the ground lines of communication, that would deflect some of the negativity right now,” the official told Reuters.

“It wouldn't automatically turn things around, but that would be an important step.”

Although the US official suggested Pakistan would have to take several steps to repair heavily damaged ties, he said the strategic allies could not afford a rupture.

“We have longer-term interests that we must keep in mind. The interests are nuclear, it is counter-terrorism and it is also reconciliation in Afghanistan for a relatively peaceful and stable region,” said the US official, who spoke on condition of anonymity.

“So you know, the heightened sentiments in Washington will eventually have to come to a point where people say hold on, we have bigger interests here.”

Pakistan, for its part, is demanding an apology from the United States over the Nato strike, but it is unlikely to get one.

The Nato strike fanned national anger over everything from covert CIA drone strikes to the US incursion into Pakistan last year to kill al Qaeda leader Osama bin Laden, and the supply routes evolved into a lightning-rod issue.

Relations with Pakistan had been poor for the past six months, said the US official.

He said both the Raymond Davis case - in which a CIA contractor shot and killed two Pakistanis he suspected of trying to rob him - and the raid on bin Laden's compound had strained ties, but the final straw was the deaths of the 24 Pakistani soldiers.

“Salala broke the camel's back,” said the US official, referring to the location where the Nato strike occurred. After six weeks of negotiations that at least once appeared close to a deal, the Pentagon acknowledged on Monday that the U.S. team had failed to clinch an accord and was coming home.

With the Pakistan routes unavailable, Nato has turned to countries to the north of Afghanistan for more expensive, longer land routes.

Resupplying troops in Afghanistan through the northern route is about 2-1/2 times more expensive than shipping items through Pakistan, a US defence official told Reuters, speaking on condition of anonymity.