US not prepared to confirm Taliban leader Mansour's death: Official

The US is not prepared to "positively confirm" that Mullah Mansour, the chief of Afghan Taliban, was killed in a drone strike deep inside Pakistan, a top official said on Sunday.

"US military took a strike, he (Mullah Mansour) was the target and at this point, we are not prepared to confirm that he was killed, though it appears likely. If that's true, that's a positive development," Homeland Security Secretary Jeh Johnson told Fox News.

"We're looking into it. At this point it's still a somewhat unfolding situation. We are not prepared to positively confirm that he's been killed," he said. Johnson said the US is assessing the results of the strike and it would be known very soon.

"I think we'll know pretty soon," he said. "We think it's significant because Mullah Mansour was actively trying to undermine efforts at reconciliation. He was targeting afghan facilities, Afghan interests and US interests. So if he was, in fact, killed this would be a major development," Johnson said in response to a question.