North Korea is preparing to launch another intermediate-range ballistic missile in next three days, Yonhap reports.
This would be the ninth test launch this year which US experts believe is timed to coincide with the US presidential elections.
The US military is worried as Musudan can be launched from concealable road-mobile launchers, typically from highways or mountainous areas.
According to the report, North Korean officials want to build a nuclear-capable intercontinental ballistic missile to strike the US. It has also shown a tendency to conduct missile launches around major events in the US. In early February, Superbowl Sunday in the US, North Korea launched a satellite into space.
One of the Musudan launches follows the final presidential debate and while top South Korean leaders visited Washington earlier this month.
"In this case, I think it's a real test," said Jeffrey Lewis, a scholar at the Middlebury Institute of International Studies specializing in North Korea. "They are going to keep firing until it works."
In March, the U.N. Security Council unanimously adopted a resolution condemning a January nuclear test as well the long range launch putting the satellite in space.
Resolution 2270 calls on North Korea not conduct further tests and immediately suspend all activities related to its ballistic missile program.
On Monday, for the first time in 28 years, a US Navy ballistic missile submarine visited the US island territory of Guam in the western Pacific. USS Pennsylvania, the American submarine which made the call to Guam, can carry 24 Trident D-5 intercontinental ballistic missiles (ICBMs) with a range of nearly 7,500 miles, capable of destroying any city in the world while submerged.
Each Trident missile can carry multiple independent warheads. Further, each one is more powerful than the atomic bomb dropped on Hiroshima during World War II.
The aim to convince North Korea to abandon its pursuit of nuclear weapons is probably a "lost cause." Last week, the Director of National Intelligence James Clapper said.