He said North Korea's most recent missile test represents "open defiance of the international community." He says North Korea poses "a grave threat" not just to the United States and its Asian allies, but also to China.
"So, this is something that we know we cannot tolerate in terms of a risk to the American people. The President has made clear that he is going to resolve this issue one way or the other. What we prefer to do his work with others, China included, to resolve this situation short of military action," he said in response to a question.
"We do have to do something, and so, we have to do something, again, with partners in the region and globally. That involves enforcement of the UN sanctions that are in place. It may mean ratcheting up those sanctions even further. And it also means being prepared for military operations if necessary," he said.
North Korea developing missile weapons and nuclear weapons capabilities are both threatening.
"Because developing a nuclear capability has to be matched to a delivery system. So, their sixth nuclear test is what it would be, combined with the ballistic missile program that poses a grave threat to the United States and our citizens, as well as our friends and partners in the region," he said.