"We certainly do respect Pakistan's territorial integrity. But as we've said before, we will carry out strikes to remove terrorist who are activity pursuing, and planning and directing attacks against US forces," the State Department Deputy Spokesman, Mark Toner, told media persons at his daily news conference.
Toner was responding to questions on Pakistan hitting out at the US for launching the drone strike on its soil to kill Mansour, describing it as a "violation of its sovereignty".
"The strike sends a clear message that those who target Americans and Afghan people are not going to be given a safe haven. And then also, that it know that there's only one option for the Taliban and that is to pursue a peaceful resolution to the conflict," Toner said in a subtle warning to the Taliban.
He said the death of Mansour does not mean defeat of the Taliban but it does send a clear message.
"What I think it does send is a clear message. If you're going to carry out attacks, if you're going to lead attacks against our forces and against Afghanistan's forces, then you are going to be targeted and you're not going to have safe haven," Toner said.
He said it also sends the message that the Taliban must decide what its future is going to be.
"Whether it's going to be part of a peaceful, political future for Afghanistan. There is a path towards that. They can sit down with the Afghan government and begin negotiations and talks. We've encouraged that. We support an Afghan-owned, Afghan led process," he said.
"I think it presents them with a clear choice. You know that there are ways to engage and identify the fact that you're willing to engage in a peaceful way. And frankly, Mansour showed no. Absolutely no predilection towards engaging in any kind of peaceful political process," he said.
Mansour, believed to be in his 50s, was killed when a US drone fired on his vehicle in the southwestern Pakistani province of Baluchistan. He had emerged as the successor to Taliban founder Mullah Mohammad Omar, whose 2013 death was only revealed last summer.
Pakistan summoned US Ambassador David Hale to express concern over the drone strike.