U.S. Joint Chiefs of Staff Chairman Mike Mullen expressed concern about the unpredictability of North Korea’s leadership.

Appearing on CBS News’ “Face the Nation,” Mullen said he's very comfortable with Washington’s defensive posture, but is increasingly concerned about North Korea's belligerence.

He said the seven missiles fired by the North Saturday are a violation of U.N. Security Council Resolution 1874 and reminiscent of similar moves made by Pyongyang in 2006.

Admiral Mullen said the international community must continue exerting pressure on Pyongyang to let it know that its actions serve only to further isolate itself.

On the North Korean ship suspected of carrying illicit weapons suddenly changing course, Mullen said it looks like the vessel Kang Nam is on its way back to North Korea. He said he’s not sure why it aborted its journey.