Islamabad: Pakistani President Asif Ali Zardari has said the United States must provide "clear terms of engagement" in the battle against Islamist militants, if strained bilateral ties are to improve.

Zardari's remarks came during talks late on Monday with Marc Grossman, the US Special Representative for Afghanistan and Pakistan, successor to late veteran diplomat Richard Holbrooke who was President Barack Obama's previous pointman on Pakistan and Afghanistan.

Relations between Islamabad and Washington have nosedived since Al Qaida leader Osama bin Laden was killed on May 2 in a clandestine raid by elite US forces in Pakistan.

Washington did not inform Islamabad about the raid, leaving Pakistan's military humiliated after the operations invited allegations of complicity in sheltering bin Laden close to the country's leading military academy.

"In the absence of well-defined and documented terms of engagement, wrong plugs may be pulled at the wrong times by any side that could undermine the bilateral relations," Zardari's office said after Monday's talks.

"The president said that terms of engagement should be clearly defined and specified so that any dispute could be settled amicably," the statement added.

The US has been pushing Pakistan to crack down on Islamist militant safe havens in tribal areas bordering Afghanistan. Many observers say elements within the Pakistani establishment support the extremist groups.

Zardari gave no further details about proposed terms of engagement, but they would likely include terms for conducting US drone strikes that routinely target militants in Pakistan's tribal areas.

The strikes have drawn scathing criticism from Islamabad over civilian casualties. Obama's administration recently suspended about a third of its $2.7 billion annual defence aid to Pakistan, but assured Islamabad it was committed to a $7.5 billion civilian assistance package approved in 2009. In the latest sign of tension, US diplomats based in Islamabad have complained about new restrictions preventing them from travelling inside Pakistan.