The United States says Pakistan's cooperation is prerequisite for success in Afghanistan, reported Radio Pakistan. 

The remarks were made by Chairman US Joint Chiefs of Staff General Joseph Dunford while responding to a question about the ongoing review of the Afghan policy at the annual Aspen Security Forum in California.

The General said the ongoing US policy review is not just about Afghanistan but also about South Asia and Iran. He said Pakistan has to be a critical element of the US strategy in the region. 

Gen Dunford said over the last two years the Afghan forces have suffered significant casualties and more work is needed to increase their ability.

Asked about a time-frame for an exit strategy, Gen Dunford said putting any artificial timeline for it would be counter-productive.