With US President Donald Trump giving South Korea the green light to build its own nuclear-powered submarine, a decision that has reignited debate in Japan on boosting its own nuclear defence capability, experts have raised concerns about escalating tensions and a potential arms race in the region.

They also foresee backlash from Russia, China and North Korea, all of which would not want the US allies to acquire more advanced underwater weapon systems that rival their military prowess in the region.

Mr Trump had announced on Oct 30 that the US will help South Korea build a nuclear-powered submarine.

This came a day after South Korean President Lee Jae Myung told him during a meeting in the south-eastern city of Gyeongju that Seoul’s current diesel-powered submarines have limited underwater navigation capabilities that restrict the military’s abilities in tracking North Korean or Chinese submarines within its waters.

The decision has since unleashed debate in Japan on whether Tokyo should follow in Seoul’s footsteps in asking for nuclear submarines, especially in the wake of a defence plan unveiled by newly minted Prime Minister Sanae Takaichi on Oct 21 that had included a push to acquire “next-generation submarines with advanced propulsion capabilities”.

Ms Takaichi’s policy speech dovetailed with a Defence Ministry expert panel’s recommendation on Sept 19 for Japan to acquire such submarines, marking the first time an official government advisory body has openly endorsed such an idea, signalling a potential seismic shift in Tokyo’s defence policy.

Both Japan’s and South Korea’s separate nuclear cooperation agreements with the US bind them to seek consent for any enrichment or reprocessing of uranium, which yields nuclear fuel.