SEOUL/TOKYO – 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.