During the past three months, several of the access roads have been re-graded and laid with gravel, suggesting preparation to handle missiles heavier than the Musudan IRBM like an ICBM, and a small 11-by-11-meter pad has been graded and gravel laid, he said.

In addition, the second launch position appears to have been regraded, although it remains unpaved, which when complete, would allow for simultaneous launches of ballistic missiles. New ground scarring a short distance from the firing positions suggests the intention to install two telemetry or camera positions, perhaps for monitoring a long-range missile test, he said.

The site has been designed and previously used to test Musudan missiles, which is also a road-mobile missile like the ICBM the North is preparing to launch, and can easily be supported by the infrastructure of the nearby Kalma airport, the expert said.

Moreover, like previous failed Musudan tests, a catastrophic failure of an ICBM would not impact North Korean soil, he said.

North Korean leader Kim Jong-un said in his New Year's Day address that the regime has entered the final stage of preparations to test-fire an intercontinental ballistic missile, an apparent threat the North is close to developing a nuclear-tipped missile capable of striking the continental US.

Officials in Seoul said last week that South Korea and the United States have picked up signs that the North placed the two missiles, less than 15 meters long, on mobile launchers in an indication that Pyongyang could carry out a threatened ICBM test earlier than expected. (Yonhap)