Islamabad: Pakistan and the US on Thursday acknowledged they were yet to resolve differences which took their ties to a new low last year and said more talks were needed to address outstanding issues like "illegal" CIA drone strikes and reopening of NATO supply routes to Afghanistan.

The outstanding issues figured in meetings between visiting US Special Representative Marc Grossman and Pakistan's civil and military leaders, officials said.

Grossman held separate meetings with army chief Gen Ashfaq Parvez Kayani, Foreign Minister Hina Rabbani Khar and Foreign Secretary Jalil Abbas Jillani.

"We consider drones as illegal, non-productive and unacceptable," Jillani said at a joint news conference with Grossman.

"This is an issue which has been discussed by the highest civilian and military leadership," he said.

Pakistan expects that talks with the US will lead to a solution of the issue under guidelines set by parliament following a recent review of bilateral relations, Jillani said.

Jillani and Grossman acknowledged that the two sides would need to hold further discussions on the reopening of supply routes to Afghanistan, which were closed after a cross-border NATO air strike on November 26 that killed 24 Pakistani soldiers.

"Let me make it clear that the arrangement with regard to the NATO supplies that existed prior to November would no more be valid. We have to work out a new arrangement. The process will begin with a direction from the cabinet," Jillani said.

The two sides will hold another exploratory meeting to look at various related issues, he added.