Mullah Akhtar Mohammad Osmani, identified as the head of Taliban operations in Helmand and Kandahar provinces, was reported killed along with two associates when their vehicle was hit in an air raid near the Pakistani border.
The strike happened on December 19.
U.S. military spokesman Colonel Tom Collins, speaking in Kabul, said the U.S. military made the announcement only today because it first wanted to verify that Osmani was among those killed.
Collins said Osmani's death is a major breakthrough that will hurt the Taliban's strategic ability.
"Mullah Osmani is the highest ranking Taliban leader that we've ever killed, he was the chief of the Taliban military operations, so his death is very significant and will hurt the Taliban's operations," Collins said. "They will no doubt reconstitute his position, they'll put somebody else in that role who'll take a while to get up to speed. But Osmani was an associate of Osama bin Laden, Mullah Omar, and [Hizb-e Islami leader Gulbuddin] Hekmatyar. He had built up relationships with key figures in their terrorist organizations, so replacing him will be very difficult."
A Taliban commander, Mullah Hayat Khan, strongly denied that Osmani was killed, saying he was not in the region at the time.