Newly named Pakistan Taliban chief may be dead - U.S.

Hakimullah had been described as even more aggressive than Baitullah.

Washington believes the Taliban has been weakened by infighting between factions vying to take command since Baitullah Mehsud's death.

"The point is there is a succession crisis going on," the defence official said, adding there were other contenders to lead the movement. "There's a variety of factions within the Mehsud tribe."

Military aircraft and artillery have been hitting Taliban targets in Waziristan for months, and it is unclear if and when ground forces will move in force.

As part of its campaign to weaken the Taliban, U.S. officials said the Pakistani army has been trying to negotiate with various factions, trying to split them off from harder-line groups loyal to Baitullah.

Several top members of his group, including one of his aides and the spokesman from the Swat valley, have also been captured in recent months.

The Pakistani army believes it has cleared nearly all of the former Taliban bastion in Swat, 80 miles (120 km) northwest of Islamabad, with an offensive launched in April.

While largely forced out of Swat and Bajaur, there are still thousands of well-armed fighters in South Waziristan and other regions.

(Editing by Simon Denyer and Todd Eastham)