The Taleban had claimed responsibility for the attack Saturday outside a combat outpost in eastern Wardak province.

But Defense Department press secretary George Little said Monday that it was Haqqani operatives. Little said it is highly likely their top leadership supported and was aware of the attack.

The Haqqani network is a Pakistan-based group affiliated with both the Taleban and Al-Qaeda. It has emerged as one of the biggest threats to stability in Afghanistan.