Top U.S. Officer: Kim Jong Un Irrational, Unpredictable

North Korean, Chinese threats marred Obama's Pacific Strategy in 2013.

In this image taken from video made available on Jan. 1, 2014, North Korean leader Kim Jong Un delivers an annual New Year's Day message in Pyongyang, North Korea.
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Last year was scarred by instability and threats in the Pacific region, particularly from North Korea and China, at a time when the U.S. is ramping up its presence and rhetoric there in President Barack Obama's notorious "rebalance."

At the top of the worst offenders list sits North Korea's Kim Jong Un. The young dynastic ruler thrust the hermetic kingdom into top headline space in 2013 following a string of visits by professional eccentric and one-time NBA superstar Dennis Rodman, and continued saber rattling over its nuclear and military programs.

[READ: U.S. Sends Troops to Korean Peninsula as Instability Grows]

America's top officer in the region expressed grave concerns Thursday about how the U.S. charts a path toward the untested and reclusive despot.

"The young leader, for unpredictable," said Navy Adm. Samuel Locklear, the commander of U.S. Pacific Command. "His behavior, at least in the way it's reported and the way we see it in sense, would make me wonder whether or not he is always in the rational decisionmaking mode or not. And this is a problem."

The communist nation conducted nuclear tests in 2006, 2009 and 2013, the last of which North Korea claims proved its ability to miniaturize the process into a warhead. It also continues to perfect its ballistic missile capabilities, and threatened in April to launch one toward the U.S. mainland.

North Korea's continued nuclearization threatens the Korean peninsula, the region, and potentially the world, says Locklear.

"The way ahead with the new leader there is not clear to me," he said at a Pentagon press briefing. "It is potentially a very dangerous place."

Locklear also offered a peek behind the scenes of the U.S. relationship with China, brought to the brink last year by the communist nation's decision to surprise the world with a new air defense zone in international space, and a near collision in December between U.S. and Chinese navy ships.

[PHOTOS: Tensions Rise Between North and South Korea]

Communication with the top echelons of the Chinese government, he said, remains untested in a catastrophe. Joint Chiefs Chairman Martin Dempsey and Defense Secretary Chuck Hagel have made occasional attempts at dialogue with their Chinese counterparts in the last year.

"Would that work in a time of crisis? We would hope it would work," Locklear said. "I don't have the ability to pick up the phone and talk directly to a [Chinese People's Liberation Army] admiral or general at a time of crisis. And we need to work on that."

China announced in November it would enforce a new "Aerial Defense Identification Zone" over a hotly contested area of the East China Sea that includes a string of islands Japan claims as its own. The U.S. immediately denounced the ADIZ and refuted China's supposed rules by flying a series of undeclared military sorties through the area.

The next month, the USS Cowpens almost collided with a Chinese warship. Defense and State Department officials blamed a lack of communication between the two militaries.

"If we keep getting surprised, we're probably not doing enough," said Locklear. The announcement of the ADIZ was not necessarily a surprise, he added, though China did not consult the U.S. or its regional allies before.

[ALSO: Unlikely Kim Jong Un Fed Uncle to a Pack of Dogs, Experts Say]

"The fact that they established an ADIZ is of less concern to me than how it was done," he said.

These potentially catastrophic incidents are paradoxical when compared to the cooperation between the U.S. and China over the last year. China participated -- albeit reluctantly -- in the military operation to provide humanitarian relief to the Philippines following Typhoon Haiyan. It plans to attend the annual RIMPAC military exercise, and is conducting security operations as far away from home as the Gulf of Aden.

"As I look at China globally, there are some positive aspects for how they're using their military force in a productive way," Locklear said. "Our bilateral relationship, I would give it a passing grade for the last year."