Former Joint Chiefs Chair Admiral Mike Mullen had a stern warning about the reckless, disruptive and unpredictable rhetoric we've heard from Trump since taking office and what it could mean for the United States on ABC's This Week:

RADDATZ: Joining me now, former chairman of the Joint Chiefs of Staff under Presidents George W. Bush and Barack Obama, Admiral Mike Mullen. Good morning, Admiral Mullen. Let me ask you right away how you would characterize the Trump presidency this last year?

ADMIRAL MIKE MULLEN: Right. I think it's been incredibly disruptive, certainly unpredictable in many, many ways. And what you talked about globally, Martha, certainly from those who is have been our friends for many years, ask questions about our commitments to them, to the region, to the leadership that we have exhibited over the last seven years and the institutions that we care about, and our enemies. Those that would do us ill seem to be able to take advantage of the uncertainty as well, and you mentioned both Russia and China, and my expectations that will continue to be the case for them as well as Iran and North Korea.

RADDATZ: Well, let me tell you what they said from the White House. H.R. McMaster, the national security adviser, who you know well, says he has been moved out of his comfort zone, as well as others in the White House, yet his advisers, according to The New York Times, argue he has blown the cobwebs off decades of foreign policy doctrine and as he approaches his first anniversary that he has learned the realities of the world in which the United States must operate.

Do you see that happening at all?

MULLEN: Well, certainly, I would say he's -- he's been incredibly disruptive with respect to the institutions, the commitments, the leadership, where we have been for the last 70 years. And I think a big question for us as the American people is whether we continue to support those institutions and all they represent in a world that is pretty chaotic, as you pointed out in your opening. And that becomes a fundamental question. And clearly, the president has chosen to try to disrupt and break those up as much as possible, create a great uncertainty. And in my view, an incredibly dangerous climate exists out there in that uncertainty with how this all ends up in -- and one in particular that is -- top of the list is North Korea.

We're actually closer, in my view, to a nuclear war with North Korea and in that region than we have ever been. And I just don't see how -- I don't see the opportunities to solve this diplomatically at this particular point.

RADDATZ: I want to drill down on North Korea in just a few minutes, but I want to go back to a month ago when you were on the show. You said you had some concerns with so many generals in the White House and elsewhere in the administration, but that they were seen as providing stability, calmness and reasoned views for the future. Given what you just said as well, do you think President Trump is stable?

MULLEN: Yeah, I don't question the stability. I just think it's the view. And I think that I have watched Secretary Mattis and General McMaster and General Kelly on the national security issues over time I think get the president to a point where he makes a decision that may be counter to his instincts. My concern is how long that actually lasts.

And in particular, that the peninsula in North Korea and will he follow through on his rhetoric? Or will we actually be able to get to a situation where it could be solved peacefully? And I'm just more inclined to see over time that the rhetoric seems to be where the president is, and that will limit the constraining ability that both Jim Mattis and H.R. McMaster and John Kelly have.