Islamabad: Pakistan's Foreign Minister said the United States risks losing an ally if it continues to publicly criticise Islamabad's performance in the war against militancy.

"You will lose an ally," Hina Rabbani Khar said in New York. "You cannot afford to alienate Pakistan, If you are choosing to do so it will be at their (the United States') own cost."   

Khar was responding to Senate testimony by the outgoing chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, who said Pakistan's top spy agency was closely tied to the Haqqani Network, the most violent and effective faction in the Afghan Taliban insurgency.   

Mullen said on Thursday that Pakistan's Inter-Services Intelligence agency (ISI) played a role in the September 13 attack on the US embassy in Kabul, supporting militants known as the Haqqani network.   

That network, he said, is a "veritable arm" of the ISI.   

The embassy attack was the latest in a series of violent episodes that have set back US efforts to bring the Afghan war to a peaceful close.   

Mullen's comments and Khar's retort mark an unusual escalation of rhetoric between the allies in the struggle against Islamist militants and, at least in public, marks a low point in their relationship.   

US-Pakistani relations had barely begun to recover from the hostility triggered by an unannounced US Special Forces raid that killed Osama bin Laden in the Pakistani city of Abbottabad in May.   

"At the operational level it will be appropriate to say that there are serious difficulties (between the two countries)," Khar said.   

In a separate interview with India's private TV channel, Khar added: "Pointing fingers at each other will not help. Finding scapegoats will not help ... We want to be a mature, responsible country that is fighting terrorism with a lot of maturity."   

The tensions could have repercussions across Asia, from India, Pakistan's economically booming arch-rival, to China, which has edged closer to Pakistan in recent years.   

A complete break between the United States and Pakistan -- sometimes friends, often adversaries -- seems unlikely, if only because the United States depends on Pakistan as a route to supply US troops in Afghanistan, and as a base for unmanned U.S. drones. Pakistan relies on Washington for military and economic aid and for acting as a backer on the world stage.   

Washington does not want to see further instability in the nuclear-armed country.   

But support in the US Congress for curbing assistance or making conditions on aid more stringent is rising rapidly. And Mullen, CIA Director David Petraeus and Secretary of State Hillary Clinton have all met their Pakistani counterparts in recent days to demand Islamabad rein in militants.

(Agencies)