Pakistan has warned the United States it risks losing an ally if the U.S. continues to accuse Pakistan's intelligence agency of supporting extremist attacks against U.S. troops in Afghanistan.

Foreign Minister Hina Rabbani Khar was responding to comments by U.S. Joint Chiefs of Staff Admiral Mike Mullen, who said Thursday Pakistan's military spy agency, ISI, is closely tied to the Haqqani network.

Khar said the U.S. could not afford to alienate Pakistan. She said to do so would be at “the cost” of the U.S. Khar's remarks were broadcast Friday in Pakistan.

Mullen told a U.S. Senate hearing the al-Qaida-linked Haqqani network, acting with support from Pakistan's spy agency, planned and conducted the assault last week on the U.S. Embassy in Kabul.

He said the ISI also supported the truck-bomb attack by Haqqani insurgents on a NATO base in central Afghan province Wardak on September 10 that wounded 77 U.S. soldiers.

Mullen said Pakistan's ISI uses the Haqqani network as a “veritable arm” to act in Afghanistan against Afghan and coalition forces and expressed concern about the impunity with which extremist groups are allowed to operate from Pakistan.

Pakistan's Information Minister Firdous Ashiq Awan told VOA that Pakistan is working for peace in Afghanistan, and that what she called “propaganda” accusing Pakistan of helping militants is meant to sabotage Islamabad's efforts.