* U.S. sees disarray in Taliban after leader's death
* Unclear if Taliban can unite again "under one banner" (Adds U.S. counterterrorism official, paragraphs 6, 9-10, 12)
By Adam Entous
WASHINGTON, Aug 12 (Reuters) - The U.S. special envoy to Afghanistan and Pakistan said on Wednesday there were signs of disarray within the Taliban in Pakistan following the apparent death of the group's leader in a missile strike.
Washington says there is a "90 percent certainty" that the Taliban leader, Baitullah Mehsud, was killed in a strike by a pilotless CIA drone earlier this month in South Waziristan. Mehsud's aides have disputed the claim and say he is alive.
"The end of Baitullah Mehsud, as we all know, is a very big deal," U.S. envoy Richard Holbrooke said, citing reports of "disarray among his people, of other factions maneuvering."
At a panel organized by the Center for American Progress, a Washington think tank, Holbrooke said the "thrashing around" by the Taliban and its allies in Pakistan was "very good news for all of us."
"There's going to be some major readjustment coming up. We don't know what it is," he said of the groups.
A U.S. counterterrorism official, speaking on condition of anonymity, said it was unclear how long the struggle within the Taliban would last.
At least seven militants were killed in northwest Pakistan on Wednesday in a clash between fighters loyal to Mehsud and his rivals, officials and residents said.
Mehsud is, or was, the leader of Tehrik-e-Taliban Pakistan, or Taliban Movement of Pakistan, an alliance of around 13 militant groups.
The counterterrorism official said it was unclear whether the Taliban would "unite under one banner again."
"Baitullah was a pretty unifying force and was able to corral all of these strong personalities. Now we're seeing a little bit of disintegrating... We will have to see how it shakes out," the counterterrorism official said.
Mehsud is blamed for a wave of bomb and suicide attacks across Pakistan, including the one that killed former prime minister Benazir Bhutto in December 2007.
The counterterrorism official said militants could respond to Mehsud's death with "revenge attacks".
With or without their leader, the official said, "these factions can still mount attacks." (Editing by Phil Stewart)