"I think we have to deliberate a very hard blow against ISIS in the Middle East, so that there is no sense of invulnerability or invincibility there. There has got to be a military defeat of them there, but there must be a much broader approach," Mattis told lawmakers during his confirmation hearing by the Senate Armed Services Committee.
"This requires an integrated strategy so you don't squeeze them in one place and they develop in another and we are really right back to square one," he said.
Mattis was responding to a question from Senator Joni Ernest, who said that the Middle East region will inevitably remain a major focal point when talking about "Islamic extremism".
"However, I do believe that we need to look at other regions around the globe and we cannot turn a blind eye to ISIS in regions outside of the Middle East such as in Southeast Asia," he said.
Its passage will demonstrate America's fundamental unity and enable a broader commitment to deal firmly with the real and growing menace, he said.
Responding to a question, Mattis said this was still his opinion.