Adm. Mike Mullen and Gen. Ashfaq Kayani, the most senior military officials from the United States and Pakistan, have met often in recent years, interacted cordially and posed together for photos intended to convey the solidity — if not always the seamlessness — of the bilateral security relationship.

This week there was no smiling photo op, and the tone of statements made separately by the chairman of the Joint Chiefs of Staff and Pakistan’s army chief was far from cordial. More than ever before, the lack of trust between the strategic partners and the gulf between their perceptions of regional threats was made palpably and publicly clear.

“There is a real difference now, a basic stalemate. Mullen has gone public, and Kayani has responded in kind,” said Imtiaz Gul, a Pakistani security analyst. He said that Washington was preoccupied with pushing back the Taliban before the summer deadline to begin troop withdrawals from Afghanistan but that Pakistan was much more worried about arch-rival India using its influence in Afghanistan to “encircle” Pakistan.

In a series of interviews with the Pakistani media, Mullen made strong and pointed statements criticizing the Pakistani intelligence agency’s support for a group of Afghan insurgents, based in Pakistan and linked to al-Qaeda, who have been responsible for many lethal attacks on U.S. and NATO forces.

Mullen told one newspaper Tuesday that the issue of Pakistan’s reported relationship with the Haqqani network was “at the core” of difficulties between the two governments. He told another newspaper Wednesday that “it is the Haqqani network which is killing Americans across the border” and that his main concern in Pakistan was going after Haqqani and al-Qaeda.

Mullen’s unusually aggressive comments reflected the increasing tension between U.S. and Pakistani security agencies in the past several months, partly over the CIA drone attacks, which are highly controversial in Pakistan, and partly over revelations of U.S. spying activities, which were highlighted by the case of Raymond Davis, a CIA contractor who was accused of killing two Pakistani men in January.

Last week, the head of Pakistan’s Inter-Services Intelligence directorate, Lt. Gen. Ahmed Shuja Pasha, visited Washington and asked CIA officials to cut back on the drone attacks and withdraw U.S. intelligence operatives from Pakistan. American officials reportedly agreed to greater transparency with Pakistan on their spy operations but refused to make major concessions on the drones, which are considered a critical element in the war against Islamist insurgents.

Many hours after the meeting between Mullen and Kayani, which one observer close to the Pakistani military described as tense and uncomfortable, the Pakistani military spokesman’s office issued a statement saying Kayani and Mullen had agreed on “addressing the trust deficit between the institutions and the people on both sides.”

The statement went on to say that Kayani had “strongly rejected negative propaganda of Pakistan not doing enough” to combat Islamist terrorism and that he had “reinforced” his government’s strong opposition to the U.S. campaign of drone strikes, which he said “not only undermine our national effort against terrorism but turn public support against our efforts.”

A Pakistani security official, speaking on the condition of anonymity Thursday because of the sensitivity of the issue, said military and intelligence officials were “highly displeased” by Mullen’s allegations and by his rejection of Pakistani demands for a scaling back of attacks by unmanned aircraft. “The way Admiral Mullen talked here, his tough stance, didn’t help at all. I would say, rather, it added to the prevailing tensions.”

The official said that Pakistani forces “consider the Haqqani network an enemy like other Taliban factions, and there should be no doubt about it.” He said launching an operation against Haqqani’s base in the North Waziristan tribal area was “only a matter of time and resources.”

Another security official said that the Pakistani army was seriously discussing such an operation but that it was insisting first on a pause in drone attacks, because “they create problems for us and make it very hard for us to convince the tribal people that we are fighting our own war.”

On the other hand, a senior army commander in North Waziristan said in a recent briefing that the U.S. drone strikes had been very effective. He said most of those killed were “hard-core al-Qaeda and Taliban terrorists,” many of them from other countries.

Late Thursday, in a deadly incident in the violence-plagued port city of Karachi, a bomb planted inside an illegal gambling club exploded, killing at least 15 people and wounding at least 35. Police said the club was frequented by criminals and was in an area marked by gang wars. No group asserted responsibility for the blast.

Special correspondents Shaiq Hussain in Islamabad and Haq Nawaz Khan in Peshawar, Pakistan, contributed to this report.