A leading British defense publication says North Korea is developing new ballistic missile systems that could threaten the continental United States.
The findings are published in the latest edition of Jane's Defense Weekly.
The magazine's editor, Ian Kemp, says Russian experts have played a key role in helping North Korea develop new missiles.
"Our research reveals that the North Koreans are working on two new ballistic missile systems, both of which appear to be derived from the Soviet R-27 submarine-launched ballistic missile," he said. "Now this was developed by the Soviets in the 1960s and was carried by Russian nuclear submarines for the later half of the Cold War. And it would appear that former Soviet, and now Russian technicians, over a period of time have helped the North Koreans develop this technology."
The magazine says a land-based version of the missile would have a range of up to 4,000 kilometers, while the submarine-launched or ship-mounted version could travel 2,400 kilometers.
Mr. Kemp says the sea-launched missile would be the most threatening.
"This would be the first time the North Koreans have had a submarine-launched ballistic missile. And of course the great advantage of a submarine-launched weapon is that you are not dependent upon the range of the weapon," he said. "The submarine itself can deploy a considerable distance and could thus threaten a large area of the continental United States, for instance."
Mr. Kemp says North Korea's efforts to build nuclear weapons and missiles are a troubling development.
"Certainly the U.S. intelligence community, the South Korean intelligence community, the Japanese, will be very concerned indeed by these developments," he said. "And certainly all three countries have warned in recent months about North Korea's nuclear aspirations."
Jane's says the next step for North Korea will be to build submarines capable of launching the new missiles. It is not clear how long that would take. But the magazine says North Korea did gain technological insight from some decommissioned Soviet submarines it bought from Japanese scrap metal dealers 12 years ago.