ARBIL, IRAQ, - US defence chief Ashton Carter said Sunday that an operation to isolate the Islamic State group in Syria's Raqa should begin in conjunction with the assault on the jihadists' Iraqi bastion Mosul.
"We want to see an isolation operation begin around Raqa as soon as possible," Carter said during a visit to Iraq's autonomous region of Kurdistan to review an ongoing offensive to retake Mosul from IS.
"We are working with our partners there (in Syria) to do that," the US secretary of defence said, adding: "There will be some simultaneity to these two operations."
Iraqi forces launched a huge operation last week to retake Mosul, the last major city in Iraq under IS control.
The United States leads a 60-nation coalition that has provided key support in the form of thousands of air strikes, training to Iraqi forces and advisers on the ground.
The loss of Mosul would leave Raqa -- the de facto capital of the jihadists' self-declared "caliphate" -- the only major city still under IS control.
Carter said the idea of simultaneous operations against Mosul and Raqa "has been part of our planning for quite a while".
He also said that destroying IS's external operations capabilities was "our highest priority".