Last week Pyongyang's powerful ministry of state security said it had foiled a plot by the USA and South Korean spy agencies to kill Kim using a biochemical weapon.
North Korea is now hung up on a narrative that the CIA and South Korea's National Intelligence Service (NIS) hired a North Korean lumberjack working in Russian Federation to detonate a biochemical weapon during a military parade to end the life of the young North Korean dictator Kim Jong Un.
Lt. Gen. Vincent Stewart, the Defense Intelligence Agency's director, said North Korea is at the same time developing a nuclear device and processing fissile material, aiming to miniaturize a device for a warhead to mount on such missiles.
An intelligence source here said it will be headed by Andrew Kim, a leading Korean-American North Korea expert in the CIA who retired early this year.
But the threat to South Korea and Japan from North Korea's shorter-range weapons is imminent, added Elleman, who said he found the DIA comments "reassuring".
A spokesman for the US State Department has confirmed the latest detention: "The security of US citizens is one of the department's highest priorities".
A statement Thursday from the mission said a "Korean-style anti-terrorist offensive will be commenced to mop up the intelligence and plot-breeding organizations of the US and South Korea".
As KCNA announced the allegations last week, it also said North Korea was embarking on a campaign to root out suspected foreign agents.
"Just because April went by without a nuclear test does not mean there won't be one in May", he said.
The North is technically still at war with the South and has no diplomatic relations with the United States, but China is its sole major ally. The North also said "a guy surnamed Han" taught Kim how to enlist accomplices.
"North Korea is a very hard country to analyze, since most information must be deduced from satellite images, what little they publish officially and from defectors", Cook wrote in the Diplomat on May 1.
"These biochemical substances were to be provided with the assistance of the CIA. while the South Korean Intelligence Service was to provide necessary support and funding for this attempt at assassination on our supreme leader".
The country's Joint Chiefs of Staff has prepared a system called the Korea Massive Punishment and Retaliation (KMPR) that would involve surgical missile attacks, exclusive special warfare units and an ability to strike North Korea's leadership if South Korea feels threatened by nuclear attack.
The North's KCNA news agency said the crimes of recent Americans detained by its authorities will soon be revealed.