The warning was sounded by the Defence Secretary Leon Panetta who on an unannounced visit to Afghanistan declared,"It is difficult to achieve peace in Afghanistan as long as there is safe havens for terrorists in Pakistan".
Singling out the Haqqani network, a al-Qaeda linked Taliban faction based in Pakistan's lawless tribal North Waziristan province, the US defence secretary said, "It is an increasing concern that Haqqani safe havens still exist on other side of the border. Pakistan has to take action from allowing terrorists in their country to attack our forces on the other side of the border."
"We are reaching the limits of our patience here," NewYork Times quoted him as telling reporters after talks with Afghan leaders .
Panetta made the strong remarks after a meeting with Afghan defence minister Abdul Rahim Wardak, on the last leg of his crucial Asian tour that also took him to Vietnam and India, but not Islamabad, in pointers to deteriorating ties between the two countries.
His comments that US was running out of patience with Pakistan, comes a day after he made clear that Drone strikes against terrorists in Pakistan would continue.
The US officials said that in talks with Pakistan Washington had made, "very clear, time and again" the need to crack down on Haqqani network.
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American officials have recently blamed the Haqqani network for brazen attacks on the Afghan capital Kabul.
Ties between once close ally have soured since US special forces killed Osama Bin Laden in a covert raid in the Pakistani city of Abbotabad.
The US and Pakistan have also been at loggerheads over Islamabad's blockade of NATO supply routes to Afghanistan for the last six months. Blockade was imposed after US Air Strikes killed 24 Pakistani soldiers last November on the Af-Pak border.
Panetta arrived in Afghanistan from New Delhi, where he brushed aside concerns that Drone strikes against leaders of al-Qaeda violates that country's sovereignty.
"We have made clear to Pakistanis that the US is going to defend ourselves against those who attack US", Panetta said."This is not just about protecting the US. It's also about protecting Pakistan. And we have made it clear that we are going to continue to defend ourselves."