Citing multiple government officials, local daily JoongAng Ilbo reported Wednesday that the two countries agreed “in principle” that South Korea could build indigenous nuclear-powered submarines as deterrence against North Korea’s evolving missile and nuclear threats.

Seoul has long sought the measure to protect itself from Pyongyang’s submarine-based ballistic missiles, but the US has remained skeptical and expressed worries it would clash with Washington’s nuclear-free initiative on the Korean Peninsula.

Under an agreement with the US struck in 2015, South Korea is banned from using its nuclear technology and materials for any military purpose. Instead, the deal allowed the enriching of uranium up to 20 percent, the threshold for developing nuclear engines for submarines. 

“Building a nuclear submarine is a key policy initiative for President Moon during his visit to the UN. It has never been achieved by any government in the past, but I think (Moon) will get agreement from the US government,” a Seoul official was quoted as saying by JoongAng Ilbo.

Capable of operating deep into North Korean waters, nuclear submarines have been considered a prime component of deterrence capabilities in monitoring Pyongyang’s nuclear facilities and striking them if an attack is imminent.

Unlike South Korea’s conventional diesel-powered submarines, which have to emerge out of the water for oxygen every three to four days, nuclear-powered submarines can engage in underwater missions for up to a year, unless they surface for their sailors or supplies.

North Korea’s successful SLBM launches in 2016 have prompted more calls for nuclear submarines, with some analysts and politicians suggesting that South Korea could avoid US restrictions by developing a nuclear submarine run by low-enriched uranium.

“We are ready to consider it,” Defense Minister Song Young-moo told lawmakers in July after North Korea succeeded in launching a Hwasong-14 missile, Pyongyang’s first intercontinental ballistic missile capable of reaching the contiguous US.

In his phone call with President Trump last month, President Moon raised the issue as a measure to boost Seoul’s own military capability. But Cheong Wa Dae official said Wednesday that there was no specific agreement during the conversation.

By Yeo Jun-suk (jasonyeo@heraldcorp.com)