But the North Korean leader has no intention of starting a war, a source close to Kim said.
Kenji Fujimoto, the former sushi chef to the current leader's father, Kim Jong Il, told Japanese newspaper Mainichi Shimbun that the younger Kim's military decisions are made spontaneously.
Fujimoto is finally breaking his silence after his recent trip to Pyongyang, where he stayed April 12-23.
The Japanese national was visiting North Korea in time for the commemoration of the "Day of the Sun," April 15, which is founder Kim Il Sung's birthday.
Fujimoto told press that Kim "has no mind to start a war," but that "every time he sends an envoy to the United States the envoy is forced to face false charges" about Pyongyang's provocations.
The former sushi chef seemed to be suggesting that Kim Jong Un was irritated by unilateral U.S. sanctions and military threats from rivals, South Korean news service News 1 reported.
But an immediate military strike wouldn't be the first option that would be considered in Washington, CBS News reported Tuesday.
In an interview with Charlie Rose, U.S. President Barack Obama said, "We could, obviously, destroy North Korea with our arsenals. But aside from the humanitarian costs of that, they are right next door to our vital ally, [South Korea]."
Building missile defense systems is key, Obama said.
But Robert Einhorn, a former special adviser for nonproliferation and arms control at the U.S. State Department, told reporters in Seoul the United States cannot rule out the use of nuclear weapons, because of the "potential threat that North Koreans pose against South Korea."
Fujimoto has a long history with the Kim family that began in the 1980s and became friendly and familiar with the young Kim Jong Un. Since leaving North Korea in 2001, he has become a vital source on the secretive North Korean leader. On his most recent trip, the two exchanged information on North Korea-Japan relations. Fujimoto told Kim Japan's view of the North is at a low point.
"[Secretary Kim] said that he thought it would be a good idea if I played a bridging role between Pyongyang and the Japanese government," he said.