Calls are growing among ruling party lawmakers for the construction of nuclear-powered submarines as the threat of North Korea’s submarine-launched ballistic missiles looms large.

North Korea successfully test-fired a SLBM last week. Launched near Sinpo on the North’s eastern coast, the missile flew some 500 kilometers and fell into waters 80 kilometers inside Japan’s air defense identification zone.

Defense officials in Seoul said it would take the North one to three years to deploy SLBMs. North Korean leader Kim Jung-un already ordered last year the construction of new submarines that can carry two to three ballistic missiles.

The North’s deployment of SLBMs would significantly amplify its nuclear threat as missiles launched from underwater are more difficult to detect and destroy.

The South’s land-based missile defense system would be useless if the North’s submarines invade deep into the south undetected and fire SLBMs from behind.

The best defense against the North’s SLBMs is nuclear-powered submarines that can keep watch for its submarines and strike before they fire missiles.

Nuclear-powered submarines can remain submerged for months, while diesel-powered ones can operate underwater for a maximum of two to three weeks.

As the North’s SLBM threat looms large, a group of lawmakers from the ruling Saenuri Party issued a statement Monday calling for the construction of submarines with nuclear propulsion. They said that the South was vulnerable to the North’s SLBMs as it is surrounded by the sea on three sides. 

Rep. Chung Jin-suk, the party’s floor leader, joined the lawmakers in urging the government to build nuclear submarines. He referred to the South Korean military’s failed attempt in 2003 -- then under President Roh Moo-hyun -- to construct 4,000-ton nuclear submarines.

The Defense Ministry remains cautious on the matter. While answering questions from lawmakers, Defense Minister Han Min-koo said his ministry would study the possibility of building nuclear submarines.

Technically, South Korea can build nuclear-powered submarines on its own. Experts say it would take the nation eight to 10 years to design and construct them. 

But the government has to take into consideration other aspects of the matter. If South Korea builds nuclear submarines, it would breach its denuclearization principle, which is enshrined in the 1992 joint declaration of South and North Korea.

South Korea has been faithful to the principle, obliging itself to use nuclear energy solely for peaceful purposes. This principle underlies the South’s demands for the North’s dismantling of its nuclear programs. Hence, if the South ditches the principle, it would undermine the foundation of its push for the denuclearization of the Korean Peninsula.

Moreover, Seoul will have to obtain cooperation from Washington in using its nuclear technology for the construction of nuclear submarines, as the Korea-US atomic energy agreement, which was revised last year, bans technology and equipment that originates from the US being used for military purposes.

Yet the government needs to find ways to address these problems and push for nuclear-powered submarines in light of increasing nuclear threats from the North. Just worrying about the threats does not enhance national security. The government needs to take action to bolster the country’s missile defense.