|Rahman was assumed to be in his mid-30s and bin Laden's close confident [EPA/US State Department]
Al-Qaeda's second-in-command was killed in Pakistan earlier this week, according to Pakistani and US officials.
Atiyah Abd Rahman died on August 22 in the tribal Waziristan region, the official told the Associated Press news agency on condition of anonymity.
The official did not give details on how Rahman was killed.
Local officials in the tribal region however told the AFP news agency last week that a US drone strike on August 22 on a vehicle in North Waziristan killed at least four people.
Rahman, a Libyan national, was the group's former operational leader until al-Qaeda leader Osama bin Laden was killed in a US raid on his Pakistan compound in May.
US and Pakistani intelligence ties have been strained since the unilateral American strike against bin Laden, and Pakistani intelligence did not confirm Rahman's death.
He was assumed to be in his mid-30s and was bin Laden's close confident, once serving as his emissary to Iran.
"Rahman's death is a tremendous loss for al-Qaeda, because Ayman al-Zawahiri was relying heavily on him to help guide and run the organisation, especially since Bin Laden’s death," the US official said.
Zawahiri had been serving bin Laden for years as a powerful and influential senior official in the group. He took over as leader after bin Laden's death, and his seat was filled by Rahman.
'Difficult to replace'
"The trove of materials from bin Laden’s compound showed clearly that Rahman was deeply involved in directing al-Qaeda’s operations even before the raid," the US official said.
|Al Jazeera speaks to Imtiaz Gul, a political analyst in Islamabad, on the reported death of Abd al-Rahman
"He had multiple responsibilities in the organisation and will be very difficult to replace."
Noman Benotman, the former leader of the Libyan Islamic Fighting Group and now an analyst with Britain's Quilliam think tank, described al-Rahman as al-Qaeda's chief executive officer.
"In the last two years he successfully, and I think more or less single-handedly, created the dynamics that kept al-Qaeda together," he said.
Rahman's real name was Jamal Ibrahim Ishtawi, Benotman said. A graduate of the engineering department of Misrata University, he left Libya to go to Afghanistan in 1988 and joined the groups then fighting Soviet occupation.
Leon Panetta, the US defence secretary, said last month on a visit to Afghanistan that he believed the strategic defeat of al-Qaeda was within reach if the US could kill or capture up to 20 remaining leaders of the core group and its affiliates.
The report of Rahman's death came as the US gears up to mark the 10th anniversary of the September 11, 2001 attacks on landmarks in Washington and New York, blamed on al-Qaeda, which killed nearly 3,000 people.