WASHINGTON (AP) -- U.S. and Pakistani officials said Saturday that al-Qaida's second-in-command, Atiyah Abd al-Rahman, has been killed in Pakistan, delivering another big blow to a terrorist group that the U.S. believes to be on the verge of defeat.

Since Navy SEALs stormed Osama bin Laden's compound and killed him in May, the Obama administration has been unusually frank in its assessment that al-Qaida is on the ropes, its leadership in disarray. Defense Secretary Leon Panetta said last month that al-Qaida's defeat was within reach if the U.S. could mount a string of successful attacks.

``Now is the moment, following what happened with bin Laden, to put maximum pressure on them,'' Panetta said, ``because I do believe that if we continue this effort we can really cripple al-Qaida as a major threat.''

A Libyan national, al-Rahman never had the worldwide name recognition of bin Laden or bin Laden's successor, Ayman al-Zawahiri. But al-Rahman was regarded as an instrumental figure in the terrorist organization, trusted by bin Laden to oversee al-Qaida's daily operations.

When the SEALs raided bin Laden's compound, they found evidence of al-Rahman's deep involvement in running al-Qaida.

Senior al-Qaida figures have been killed before, only to be replaced. But the Obama administration's tenor reflects a cautious optimism that victory in the decade-long fight against al-Qaida could be at hand.

``It does hold the prospect of a strategic defeat, if you will, a strategic dismantling, of al-Qaida,'' incoming CIA Director David Petraeus said in July.

Since bin Laden's death, counterterrorism officials have hoped to capitalize on al-Qaida's unsettled leadership. The more uncertain the structure, the harder it is for al-Qaida to operate covertly and plan attacks.

Al-Zawahiri is running the group but is considered a divisive figure who lacks the founder's charisma and ability to galvanize al-Qaida's disparate franchises.

A U.S. official, who spoke on condition of anonymity to summarize the government's intelligence on al-Rahman, said al-Rahman's death will make it harder for Zawahiri to oversee what is considered an increasingly weakened organization.

``Zawahiri needed Atiyah's experience and connections to help manage al-Qaida,'' the official said.

Al-Rahman was killed Aug. 22 in the lawless Pakistani tribal region of Waziristan, according to a senior administration who also insisted on anonymity to discuss intelligence issues.

A Pakistani intelligence official said al-Rahman died in a U.S. missile strike in Machi Khel village in North Waziristan on Aug. 22.

The U.S. official would not say how al-Rahman was killed. The Pakistani official did not say how the country's main intelligence agency, the ISI, knew that al-Rahman was dead. This official did not give his name in keeping with agency rules.

Intelligence officials had said at the time that four people were killed in the attack.

But a CIA drone strike was reported that day in Waziristan. Such strikes by unmanned aircraft are Washington's weapon of choice for killing terrorists in the mountainous, hard-to-reach area along the Pakistan-Afghanistan border.

Al-Rahman has been thought to be dead before. Last year, there were reports that al-Rahman was killed in a drone strike; neither U.S. officials nor al-Qaida ever confirmed them. The officials who confirmed the death Saturday said it represented the consensus opinion of the U.S. government.

Born in Libya, al-Rahman joined bin Laden as a teenager in Afghanistan to fight the Soviet Union.

He once served as bin Laden's personal emissary to Iran. Al-Rahman was allowed to move freely in and out of Iran as part of that arrangement and has been operating out of Waziristan for some time, officials have said.