Fresh from meetings in Kabul, she was to be joined in Islamabad by CIA chief David Petraeus and the top US military officer, Martin Dempsey. They will meet top civilian and military leaders in the capital.

Pakistan has long seen US leaders as divided between "good cop and bad cop", but the Clinton-Petraeus-Dempsey troika is a rare joint showing designed to present a united American front in its dealings with Pakistan.

"There exists a serious trust deficit between the two countries and we hope that all issues of concern will be thoroughly discussed," a Pakistani security official told AFP.

"When the Americans ask us to do more, why don't they try to understand our problems and address our reservations and concerns?" said the official, calling for an understanding "written out in black and white" to avoid future problems.

"Pakistan will tell the Americans that the military options are getting limited in Afghanistan and there is a need to promote a genuine Afghan-led peace process through dialogue involving all the stakeholders," he added.

Copyright AFP (Agence France-Presse), 2011