U.S. Defense Secretary Ash Carter said on Friday that U.S. will use “boots on the ground” to take back the cities Mosul and Raqqa and fight ISIS militants.

“We need to destroy them in those two places, and I’d like to get on with that as soon as possible,” Mr. Carter, speaking from Davos, Switzerland, said in an interview on CNBC.

He said the U.S.-led coalition against the ISIS militants is using raids and bombs to take control of the routes between the two cities and cut off communication between them.

“That’ll essentially separate the Iraqi theater from the Syrian theater,” he said.

He also said that more ground troops will probably be added to support the existing forces, but it is more possible to use local forces “rather than trying to substitute for them.”