North Korea's leader Kim Jong-un, center, speaks while inspecting a newly built submarine at an unknown location in North Korea, in this undated photo provided July 23, 2019, by the country's state-run Korean Central News Agency. AP-Yonhap

By Jung Da-min

Among the messages from North Korea to the outside world during the 8th ruling Workers' Party of Korea (WPK) Congress which kicked off last Tuesday, defense watchers paid attention to remarks by the country's leader Kim Jong-un on his regime's nuclear war deterrent and self-reliant defense capabilities.

In particular, an article by the state-run Korean Central News Agency which reported Kim had told the congress that "the design of the country's new nuclear-powered submarine was researched and was in the stage of final examination" drew attention. This was the first time for Pyongyang to admit that it was developing a nuclear-powered submarine.

Defense experts said development of such a submarine would take at least several more years and thus does not pose an imminent threat to South Korea or any other neighboring countries. But, they said if successfully developed, it would enable North Korea to strike U.S. territories, with its capability to operate submerged for months.

"North Korea's current capabilities related to submarine launched ballistic missiles (SLBM) do not pose an imminent threat to the United States, as the ranges of its SLBMs are rather short while most of their submarines are diesel-powered which cannot operate submerged for a long period of time as they need to resurface to refuel," said Moon Sung-mook, a senior researcher at the Korea Research Institute for National Strategy.

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"This was why the country's leader Kim Jong-un wanted to develop nuclear-powered submarine. ... Although Pyongyang's development of a nuclear-powered submarine will take several more years as so far it has only completed the design and still needs to conduct more procedures including testing, it still poses a threat to the U.S. in that it could directly target U.S. territories once developed."

Moon said as North Korea has conducted six nuclear tests it could more easily secure enriched uranium than the South, which has also been pushing ahead with a plan to procure a nuclear-powered attack submarine.

Another defense expert Shin Jong-woo, a senior researcher at the Korea Defense and Security Forum, said it will take many more years for North Korea to finish the development of nuclear-powered submarine, as it requires many advanced technologies aside from securing enriched uranium.

"When it comes to building a nuclear-powered submarine, we not only need to put nuclear power in it but also develop technologies to reduce noise, and other combat systems to be installed," Shin said. "But North Korea's current technologies related to submarines are rather outdated, as seen in the 2000- and 3000-ton vessels the country has so far unveiled."

Shin said North Korea wants to send a message to the United States with the new President-elect Joe Biden administration set to be inaugurated soon that it will push ahead with weapons development if it does not see the progress it wants in denuclearization negotiations with the U.S.