Mullen: North Korea More Likely Than Any Other Foreign Policy Challenge to Have 'Explosive Outcome'

The former chairman of the Joint Chiefs of Staff who bridged the Bush and Obama administrations warned that the most potentially explosive security issue the incoming administration will have to deal with is North Korea and nuclear weapons.

Retired Adm. Mike Mullen, who served as chairman from 2007 to 2011 and is now a professor at Princeton University, said the presidential transition entails "leaving campaign rhetoric behind and the reality of governing, which just hits you square in the face."

"And so focusing on, finding out and focusing on the real issues that are facing the current administration and then developing policies and strategies, if you will, to meet those challenges," he told ABC this morning.

Mullen said he's "encouraged, actually" by the fact that Donald Trump "is turning to people" who have adequate foreign policy experience.

"And that will really make a difference. The world is very unforgiving. And he has said, rightfully so, that he wants to focus here in the United States," he said. "But I've always found, certainly in my time, that challenges that exist internationally, whether it's North Korea or China or Russia or the Middle East, will certainly be on his desk on day one."

Mullen singled out the Korean peninsula as "more likely than anyplace else in the world to potentially create an explosive outcome, particularly tied to the North Korean leader Kim Jong-un."

"Realize that he has nuclear weapons and the inability so far to contain him in that regard. And that's a place where four of the five top economies in the world are centered. Stability there is critical, and at least North Korea historically has generated a surprise, if you will, for new leaders in this country," the admiral continued, acknowledging that neither the Bush policy nor the Obama policy succeeded at reining in the regime.

"I think actually this has to go through Beijing. And Beijing has pushed back on that time after time... we're going to get to the point where he's going to be able to put a nuclear weapon on top of an intercontinental ballistic missile that could hit the United States, and that's unacceptable."

Mullen said retired Lt. Gen. Michael Flynn, former director of the Defense Intelligence Agency and a strong Trump supporter said to be the president-elect's pick for national security advisor, was a "terrific intelligence officer," but "now he's at the hub of the national security apparatus and he's got to be an honest broker."

"He's got to present all opinions. He has to actually -- he and his deputy have to make the trains run on time in the White House," Mullen said. "The number of issues are extraordinary and he has got to be able to do that to give the president and the cabinet, but really the president, all the options in a way where the president can make the best decision for the security of the country."