ABC News reports:

Al Qaeda has named a former deputy to Osama bin Laden as its new terror leader following bin Laden’s death at the hands of U.S. Navy SEALs in May, the organization announced on a jihadi website overnight.

Ayman al-Zawahiri, the Egyptian-born doctor who turns 60 on Sunday, was identified in the statement as the group’s new emir in a “new era” for al Qaeda — the group he helped found with bin Laden.

Earlier this month, al-Zawahiri appeared in a video in which he vowed to avenge bin Laden’s death “blood for blood.” In that video, he urged his followers to remember the 9/11 terror attacks, saying the attacks “destroyed the symbol of American economy in New York and the symbol of American military might in the Pentagon.”

Al-Zawahiri was long believed to be a leading contender to take over al Qaeda, though it took the organization more than a month to announce the transition. Noman Benotman, a former al Qaeda member and close associate of al-Zawahiri’s in the 1990s, told ABC News the delay is a sign there were likely disputes within al Qaeda over al-Zawahiri’s leadership.

In a press briefing only hours after bin Laden was killed, senior White House officials told reporters al-Zawahiri would likely not be able to stop a “path of decline” for al Qaeda.

“As the only al Qaeda leader whose authority was universally respected, [Osama bin Laden] also maintained his cohesion, and his likely successor, Ayman al-Zawahiri, is far less charismatic and not as well respected within the organization, according to comments from several captured al Qaeda leaders,” one senior official said. “He probably will have difficulty maintaining the loyalty of bin Laden’s largely Gulf Arab followers.”

However, Benotman said al-Zawahiri is a master political in-fighter and a supreme organizer of war. His first order of business, Benotman said, is to “decontaminate the group’s reputation in the Muslim world” — a reputation mired by the killing of Muslim civilians and al Qaeda’s lack of participation in the Arab Spring.