WASHINGTON - Taliban leader Mulla Akhtar Mansour was killed in a US drone strike because he represented a “specific imminent threat” to US and coalition forces in Afghanistan, the Pentagon said Monday.

“They were specific things that we knew he had engaged in or was preparing to engage in, that were were directly threatening coalition and US forces,” said Navy Captain Jeff Davis, a Pentagon spokesman.

US President Barack Obama confirmed Monday that the Afghan Taliban leader was killed Saturday in the drone strike in Pakistan. The United States and NATO official ended combat operations against the Taliban in December 2014. But their forces are still authorized to carry out “defensive” strikes against Taliban fighters who pose a direct threat to US or coalition troops. In the Pentagon’s view, the operation against Mansour was strictly in keeping with the rules, and not a sign that the United States was re-engaging the group militarily. “This is not a change in authorities at all, this is us continuing what we’ve been doing, which is conducting strikes of a defensive nature,” Davis said.

Mansour had led the Taliban since last summer’s surprise announcement of the death of Mullah Omar, the movement’s founder. Initially considered a proponent of peace talks, Mansour had led the group’s biggest military advances since the Taliban’s fall from power in Kabul in 2001. The United States still has about 9,800 troops in Afghanistan, mainly in advisory and support roles with Afghan government forces.