Pakistan and the US appeared headed for a fresh collision course as foreign minister Hina Rabbani Khar on Friday lashed out at America for accusing the country’s powerful spy agency ISI of ties with terror groups, warning it risked losing Islamabad as its ally.

"We have conveyed to the US that you will lose an ally. You cannot afford to alienate Pakistan, you cannot afford to alienate the Pakistani people," she said, adding "If they are choosing to do so, it will be at their own cost."

Khar's remarks came a day after US military chief Admiral Mike Mullen accused the ISI of supporting the Haqqani network in carrying out a string of deadly terror attacks, including an assault on the US embassy in Kabul on September 13.

He said the Haqqani network, a powerful faction of the Taliban, was a "veritable arm" of Pakistan's spy agency.

Mullen's tough words marked the first time a US official had linked ISI directly to these terror groups, signaling a significant change in the American approach to Islamabad.

The Pakistan foreign minister, who is in New York to attend the UN General Assembly meeting, told Geo News channel that though militants based in Afghanistan had carried out cross-border attacks on Pakistan, Islamabad had not resorted to a blame game even though US forces are responsible for security on the Afghan side.

It is in the interest of both Pakistan and the US to retain their relationship, Khar said. "So, if it is not a relationship of complete equals, them being a superpower and us not, but it is (a relationship) of sovereign equals."

Both countries need each other and Pakistan wants its relationship with the US to remain intact, she said. But Pakistan’s sovereignty must be respected by the US, she added.

Pakistan is fighting the war on terror in its own interest and the US may be a superpower but Pakistan is not dependent on it alone, Khar contended.

"Our Pakistani brothers and sisters should know that their country is not dependent on America, there is no economic or military dependency. Assistance has been coming from them and we would want this aid to come in a better way," she said.

At the same time, Khar acknowledged that there were "serious problems" between the two countries.

"At the operational level, it will be correct to say that there are serious problems," she said. "It will be in Pakistan's interest to preserve its national interest and remain as much a part of this relationship as them (the US)."

Khar said she had only sought "market access" during her recent meetings with American leaders and "not more assistance".

Mullen's accusations and Khar's response reflect an escalation in the war of words between the troubled allies in the war on terror.

The relationship between the two countries has been bumpy since the beginning of this year, when a CIA contractor was arrested in Lahore for gunning down two men linked to the ISI.

The ties plunged to a new low after the covert US raid that killed Osama bin Laden in the Pakistani garrison city of Abbottabad on May 2.

Since then, the US has stepped up pressure on Pakistan to act against the Haqqani network, which is based in the North Waziristan tribal region.