ISLAMABAD — A U.S. missile strike in Pakistan has killed al-Qaida’s operations chief for the country, U.S. officials said Thursday, further shredding the terrorist group’s upper ranks as it struggles to cope with the death of its founder.

Abu Hafs al Shahri was said to be in line for increasingly important duties as other senior leaders were eliminated around him. In May, U.S. special forces killed Osama bin Laden in Pakistan, and a drone attack in August killed al-Qaida’s new deputy leader, Atiyah Abd al Rahman. Earlier this month Pakistani forces arrested the head of the group’s operations against the West, Younis al Mauritani.

Experts on al-Qaida said the strike reflected a closer working relationship against the terrorist group among Afghanistan, Pakistan and the United States, despite U.S.-Pakistani tensions over the bin Laden raid, in which American troops attacked a target in Pakistan without notifying the country’s authorities in advance.

“Al-Qaida is withering away in the Afghanistan and Pakistan region,” said Rasul Bakhsh Rais, a professor of politics at the Lahore University of Management Sciences. “With this new technology and this greater cooperation between Afghanistan, Pakistan and the United States, al-Qaida doesn’t stand a chance of regrouping.”

Still, while U.S. drone strikes in Pakistan’s tribal area, which borders Afghanistan, have decimated al-Qaida’s “core” leadership — made up almost entirely of Arabs — the group’s local affiliates remain deadly and potent, especially the Pakistani Taliban.

Thursday, a suicide bomber struck a funeral, during prayers, in the Lower Dir region in Pakistan’s northwest, killing at least 31 people. They were targeted for being from a tribe that opposes the Pakistani Taliban. Similarly, four schoolchildren were gunned down in the northwest earlier this week for being from a clan that has resisted the Pakistani Taliban.

U.S. officials think that Ayman al-Zawahri, an Egyptian who succeeded bin Laden as al-Qaida chief, is hiding in Pakistan, most likely in the tribal area. Al-Qaida made the tribal area its base after the U.S.-led invasion chased the group out of Afghanistan in late 2001.

“Al-Qaida’s made a lot of mistakes since bin Laden’s death. They are now reduced to being like any other Middle Eastern criminal group, no more than that,” said Mehmood Shah, an analyst who was formerly a senior security official in the northwest. “Zawahri doesn’t have the same stature as bin Laden.”

A U.S. official, who spoke only on the condition of anonymity because drone strikes are classified operations, confirmed Shahri’s death. He described Shahri as al-Qaida’s chief of operations in Pakistan, and said he had played a key operational and administrative role for the terrorist network.

Shahri worked closely with the Pakistani Taliban, aiding it in launching attacks in the country, the U.S. official said.

An analyst who follows al-Qaida closely and who didn’t want to be identified because of the sensitivity of the issue said Shahri was a Saudi who once served in bin Laden’s security squad and now supervised military training for al-Qaida members in Pakistan and Afghanistan.

Drone strikes have quadrupled under the Obama administration, as Washington focused on the problem of al-Qaida in Pakistan’s tribal area, a largely lawless zone. Since January 2008, drones have killed 25 mid- and senior-level commanders of the core organization. The drones, operated over Pakistani territory by the CIA, are highly controversial in Pakistan, however, where it’s widely believed that hundreds or even thousands of civilians also have been killed in the strikes, a claim Washington rejects.

The U.S. operation to kill bin Laden in the northern Pakistani town of Abbottabad turned tension between Islamabad and Washington into outright hostility.

Pakistani intelligence claims that al-Qaida’s top commanders, including al-Zawahri, have now fled the drones to safer countries such as Yemen and Somalia, but U.S. officials said this week that there was no evidence that al-Zawahri had left Pakistan.

Among al-Qaida leaders probably still in Pakistan are Saif al Adel, the group’s long-term military commander, Abu Yahya al Libi, a leading al-Qaida ideologue, Adam Yahiye Gadahn, an American who is said to run al-Qaida’s media arm, and Adnan Gulshair el Shukrijumah, who grew up in the United States and whom some consider the organization’s operations chief.