“With ISI support, Haqqani operatives planned and conducted that truck bomb attack, as well as the assault on our embassy,” Admiral Mullen said in a hearing of the Senate Armed Services Committee. “We also have credible evidence that they were behind the June 28th attack against the Intercontinental Hotel in Kabul and a host of other smaller but effective operations.” In short, he said, “the Haqqani network acts as a veritable arm of Pakistan’s Inter-Services Intelligence agency.” His remarks were part of a deliberate effort by American officials to ratchet up pressure on Pakistan and perhaps pave the way for more American drone strikes or even cross-border raids into Pakistan to root out insurgents from their havens. American military officials refused to discuss what steps they were prepared to take, although Admiral Mullen’s statement made clear that taking on the Haqqanis had become an urgent priority.

On Thursday, Rehman Malik, Pakistan’s interior minister, rejected accusations by the United States of ISI involvement in the attacks in Afghanistan. “If you say that it is ISI involved in that attack, I categorically deny it,” he said in an interview with Reuters. “We have no such policy to attack or aid attack through Pakistani forces or through any Pakistani assistance.” He also said his government would “not allow” an American operation aimed at the Haqqani network in North Waziristan, a remote part of Pakistan’s lawless tribal region.

Mr. Malik seemed to indicate that American officials had threatened on Tuesday in meetings in Washington with the head of the ISI, Lt. Gen. Ahmed Shuja Pasha, that American troops were prepared to cross the border from Afghanistan to attack Haqqani militants. An American official would say only that David H. Petraeus, the new director of the Central Intelligence Agency, told General Pasha that the C.I.A. would continue its campaign of drone strikes against the Haqqanis in Pakistan and pursue them in Afghanistan.

“The Pakistan nation will not allow the boots on our ground, never,” Mr. Malik said in an interview with Reuters. “Our government is already cooperating with the U.S. — but they also must respect our sovereignty.”