Updated 4:55 p.m. ET
An al Qaeda-affiliated website says Egypt-born Ayman al-Zawahiri has succeeded Osama bin laden as head of the terror network.
Bin Laden was killed in a U.S. commando raid in Pakistan last month. Al-Zawahiri, who will turn 60 next week, had been bin Laden's second in command.
CBS News security analyst Juan Zarate says al-Zawahiri's promotion is by no means a surprise, as the Egyptian has long been a an ideological and strategic heavyweight for the group.
Zarate predicts that al-Zawahiri will likely focus on trying to keep al Qaeda cohesive and relevant as democratic uprisings sweep the Arab world and challenge the group's violence-based ideology.
He is likely to do that, says Zarate, by seeking to launch new attacks against the U.S. -- to both prove his leadership and to demonstrate a reprisal for the death of his boss.
But top administration official downplayed al-Zawahiri's selection Thursday. Defense Secretary Robert Gates said that the new al Qaeda boss lacks the charisma and operational skills of Osama bin Laden.
But he said the selection of al Qaeda's former No. 2 to take bin Laden's place is a reminder that the terror group is still out there and must be pursued.
"Despite having suffered a huge loss with the killing of bin Laden and a number of others, al Qaeda seeks to perpetuate itself, seeks to find replacements for those who have been killed and remains committed to the agenda that bin Laden put before them," Gates told Pentagon reporters, at what was billed as his last scheduled press conference before retiring at the end of the month.
Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said al-Zawahri's move to the top was no surprise, and the new leader will get the same attention from the U.S. that bin Laden did.
"As we did both seek to capture and succeed in killing bin Laden, we certainly will do the same thing with Zawahri," Mullen said.
Bin Laden was killed in a raid by U.S. Navy SEALs deep into Pakistan on May 2, scoring a treasure trove of computer data and intelligence.
Al-Zawahri, an Egyptian doctor, is known as a divisive figure who won't be the same kind of powerful inspirational leader that bin Laden was.
Gates and Mullen said they read little into the fact that it took seven weeks for al Qaeda to name a successor.
Gates quipped, "It's probably tough to count votes when you're in a cave."
Al-Zawahiri lacks strong leadership skills and his ascension will likely generate criticism, if not alienation, among al Qaeda's rank and file, the official said. Indeed, it would be difficult for anyone to lead the militant group as it continues to lose key members responsible for planning and executing attacks, the official noted.
Al-Zawahiri was last heard from in a video released on June 8, eulogizing bin Laden and vowing that the slain terror chief would continue to "terrify" America even in his death.
In spite of al-Zawahiri's menacing rhetoric, analysts say the long delay in al Qaeda naming a replacement for bin Laden, and the nature of his long-time deputy's recent video message, suggest the group's weakened position after years on the run and reported internal divisions.
Zarate called the absence of an immediate takeover "quite significant."
He said the long delay "suggests that there are internal divisions within al Qaeda's leadership and movement."
"Zawahiri is not necessarily well-liked, not charismatic. Bin Laden was the founder, the glue of this movement. And the fact that you haven't seen a new leader emerge really does suggest that there are internal fissures and friction within the al Qaeda leadership."
CBS News Islamabad bureau chief Maria Usman reports al-Zawahiri's new position does have many inside Pakistan worried, as he's seen as someone who may have the sway to bring the various militant factions together.
"He is an ideologue and tactical strategist like bin Laden," explains Usman. "His strategy has always been to hit Pakistan first in order to establish a strong base for the organization here. He and bin Laden shared the view that the main bases for al Qaeda should be Pakistan and Yemen."
CBS News terrorism consultant Jere Van Dyk was doubtful, prior to Thursday's announcement, that al-Zawahiri possessed the one key ability likely to be sought by al Qaeda in choosing a new leader: fund raising power.
Van Dyk explained that a large share of al Qaeda's funding is still believed to come from wealthy donors in Saudi Arabia, where al-Zawahiri, an Egyptian, likely has much less appeal.
He is the son of an upper middle class Egyptian family of doctors and scholars. His father was a pharmacology professor at Cairo University's medical school and his grandfather was the grand imam of Al-Azhar University, a premier center of religious study.
The announcement was posted Thursday on a website known to be affiliated with the terror network.
He and bin Laden first crossed paths in the late 1980s in the caves of Afghanistan, where al-Zawahiri reportedly provided medical treatment to bin Laden and other Islamic fighters battling Soviet forces. Their alliance would develop years later into the terror network blamed for America's worst terror attack in its history.