South Korea should develop and build nuclear weapons as a means to defend itself from the growing nuclear threat from North Korea, the mayor of Seoul, Oh Se-hoon, said in an exclusive interview with Reuters published on Monday.

South Korea doesn’t have a domestic nuclear weapons program, but the recent tensions over increased threats from North Korea have intensified calls from some politicians in South Korea that the south needs to be able to defend itself.

“North Korea has nearly succeeded in miniaturizing and lightening tactical nuclear weapons and secured at least dozens of warheads,” Oh told Reuters in an exclusive interview.