Asked during a Senate budget hearing whether he wouldrecommend halting aid to Pakistan, Panetta said: “I’d be very careful about just shutting it down.”

“What I would do is look at conditions for what we expect them to do,” Panetta said, without elaborating. He agreed to help write a letter to Congress with his recommendations for how to proceed with aid for the Pakistani military and government.

The comments came less than a week after Panetta, on a trip to Kabul, said the United States was reaching the limits of its patience with Pakistan because of the safe havens the country offered to insurgents fighting in neighbouring Afghanistan.

The American war effort there has become more costly, Panetta said on Wednesday, because of Pakistan’s decision last November to ban trucks from carrying supplies to Nato forces in landlocked, neighbouring Afghanistan.

That forced Nato to use longer, more costly routes through northern countries. Panetta told Congress that the United States was spending about $100 million a month “because of the closure of the (routes).”

It was not immediately clear how much of the $100 million was additional cost. The Pentagon has previously estimated that it cost between two and three times more to send supplies through the so-called Northern Distribution Network, but declined to offer a dollar figure on the costs.

“It’s very expensive because we’re using the northern transit route in order to be able to draw-down our forces and also supply our forces,” Panetta said.However, defense officials say the team is ready to return on short notice, and that dialogue with Pakistan is continuing.

“We hope that the (supply routes) are reopened soon, and we look forward to having our officials go back to Islamabad to seal the deal at some point in the near future,” Pentagon press secretary George Little said Tuesday.

“We’ve reached, in many respects, agreement across a range of technical issues. So we have a few more to work through, and we believe we can get to yes with the Pakistanis at the end of the day on the [supply routes. And we hope that day comes sooner rather than later,” he said.

Another American newspaper on Wednesday reported that Defense Secretary Panetta’s harsh comments against Pakistan in Kabul last week have complicated the process of negotiations on revival of Pakistani supply routes.

According to The Boston Herald, US and Pakistani negotiators had been putting the final touches when Panetta, speaking in Kabul on Thursday, said the US was “reaching the limits of our patience” over Islamabad’s failure to root out Afghan insurgents in its tribal areas, the officials said. In the wake of his comments, Pakistani officials refused to meet with a senior Defense Department official over the weekend in Islamabad, and the Pentagon announced Monday that it was bringing home a negotiating team that had worked in the Pakistani capital for nearly two months to end the bitter impasse over the supply routes.

The paper said a key sticking point remains a Pakistani demand that the US apologise in public for the Salala attack, which killed 24 Pakistani soldiers. US officials have repeatedly expressed regret and condolences over the deaths but have balked at issuing a formal apology for an incident that, in their view, involved mistakes by both sides.

The US and its allies have adjusted to the closing of the ground routes in Pakistan by moving more military supplies by air and railroad through Russia and other countries north of Afghanistan.

Meanwhile, US Senator Paul Rand was blocked from attaching an amendment to the farm bill that would withhold US aid to Pakistan. The amendment would have defunded US aid to Pakistan until the country frees an imprisoned doctor, who worked for CIA in hunt for al-Qaeda chief Osama bin Laden.

In a difficult and volatile climate against Pakistan in the US Congress - getting worse each day with the NATO supply lines lying closed - this was seen as a very challenging task for the Pakistani Embassy here in Washington.

The Pakistani ambassador had been seen on the Capitol Hill all week, lobbying non-stop with American senators and staffers, yet even getting the amendment blocked on grounds of relevance was an uphill task.

Ambassador Rehman and her senior colleagues were seen thanking all those who assisted behind-the-scenes in getting this important amendment blocked.

A Senate staffer who had been working closely with the Embassy said “It is important to note that after July, when the election campaign goes into full gear, many more such amendments are expected, and will be practically impossible to block or defeat once they get tacked on to foreign assistance clauses.

Despite what we or the Embassy says here, the mood against Pakistan is getting very negative over the last seven months. Right now, we were able to help Pakistan because the amendments could be knocked out for technical clauses, and Ambassador Rehman has left no stone unturned there! “