The Pakistani cabinet has ordered their officials to finalise a deal as soon as they can in order to bring an end to a six-month blockade on Nato supplies through Afghanistan border.
But the cabinet stopped short of announcing when the lines will reopen.
Qamar Zaman Kaira, information minister, said on Wednesday that "there is no deadline" for the talks, but added: "All departments have been asked to conclude their negotiations in the quickest possible time."
The US state department commented that "considerable progress" had been made on ending the blockade.
But "there are a number of technical issues that we are still working through", Victoria Nuland, state department spokeswoman, said
Pakistan had confirmed its president will attend a summit of NATO leaders this weekend in Chicago as negotiations with US to reopen supply lines into Afghanistan continues.
Nadeem Hotiana, a Pakistani embassy spokesman in Washington DC, said on Tuesday that Asif Ali Zardari would attend the May 20-21 summit.
Pakistan, which has endured a stormy diplomatic relationship with the US, closed the route in protest against the killing by US warplanes of 25 of its troops. Washington expressed regret for the incident and has been quietly urging Islamabad to reopen the route.
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In a statement, Oana Lungescu, a NATO spokesman, said: "This meeting will underline the strong commitment of the international community to the people of Afghanistan and to its future. Pakistan has an important role to play in that future."
But ties between Islamabad and Washington had gone from "from bad to worse", Al Jazeera's Kamal Hyder reported from the Pakistan capital.
He said Pakistan had come under "a bit of pressure" from NATO members like Turkey, a major Islamabad ally, to reopen the route.
The killing of the soldiers fanned national anger over everything from covert CIA drone strikes to the US incursion into Pakistani territory last year to kill al-Qaeda leader Osama bin Laden.
Karzai to attend
Hamid Karzai, the Afghan president, is also expected to attend the meeting, where NATO nations will hone their plans to withdraw most of their troops by the end of 2014.
As the Western presence ebbs, Pakistan, whose tribal areas are home to the Taliban and other groups, will be key in shaping Afghanistan's future.
But the supply routes have been a major sticking point.
After weeks of talks between US and Pakistani officials in Islamabad, a Pentagon spokesman George Little said he hoped that an agreement would occur in the "very near future."
Nuland said officials were still negotiating. She said a deal before next week's NATO summit would be a "wonderful signal", but that the alliance decided that Pakistan should participate regardless of whether an agreement is finalised.