ISLAMABAD — Pakistani officials warned they could jettison the United States as an ally if U.S. officials continue to accuse Pakistan's intelligence agency of helping a militant group in recent attacks in Afghanistan.

Foreign Minister Hina Rabbani Khar cautioned the United States against airing accusations such as the charge of collusion between Pakistan's Directorate for Inter-Services Intelligence, or ISI, and the extremist Haqqani network made Thursday by Adm. Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, before the Senate Armed Services Committee.

"You cannot afford to alienate Pakistan, you cannot afford to alienate the Pakistani people," Khar said, speaking on a Pakistani television channel in New York.

Pakistani army chief Gen. Ashfaq Parvez Kayani called Mullen's remarks "very unfortunate and not based on facts."

Pakistani officials rejected the accusations and challenged the United States to furnish evidence of ties between the ISI and the Haqqani group.

Mullen called the Haqqani group "a veritable arm of the ISI" and said the agency helped Haqqani extremists during attacks on the U.S. Embassy in Kabul on Sept. 13 and in a truck bombing in Wardak Province two days earlier that injured 77 American troops. U.S. military officers and former officials say Pakistan's intelligence agency communicated with Afghan insurgents who attacked the U.S. Embassy and NATO headquarters and appear to have provided them with equipment.

U.S. officials have long said privately that Pakistani intelligence aids the Haqqani network. But Mullen's comments were the most serious and specific yet, and they followed recent warnings by other U.S. officials that the United States would resort to unilateral action against the Haqqanis if Pakistan did not take them on.

Kayani's statement gave no indication that the Pakistani army, which has received billions of dollars in U.S. aid over the past decade, plans to do so.

A senior State Department official said Friday that the country had a "vital interest" in continuing to work with Pakistan to fight terrorism. "These are problems that threaten both of us," said the official, who asked not to be identified.

Estimated to number more than 10,000 fighters, the Haqqani network uses Pakistan's North Waziristan tribal region along the Afghan border from which to launch suicide bombings, commando-style assaults and other strikes on U.S., NATO and Afghan forces in eastern Afghanistan and in the capital, Kabul. The group has never carried out any attacks against targets inside Pakistan.

As U.S. pressure increased this week, Pakistani officials have accused the United States of trying to transfer blame for its faltering war in Afghanistan. Pakistani military officials said the Haqqanis are now based in eastern Afghanistan and NATO forces are also at fault for not halting fighters before they arrive in Kabul to carry out attacks.

"If the U.S. is so sure about the Haqqanis' long-distance travel to Kabul, why don't they use drone strikes against them," said one senior military officer, who asked for anonymity. "The problem lies in Afghanistan."

Material from The Washington Post is included in this report.