U.S. President Donald Trump has approved South Korea’s plan to build nuclear-powered submarines, a move that would make Seoul one of the few nations with such capabilities.

Trump met South Korean President Lee Jae Myung on Wednesday in Gyeongju ahead of the Asia-Pacific Economic Cooperation (APEC) summit. Seoul’s presidential aide said the two countries reached a broad agreement covering investment and shipbuilding, which Trump described as “pretty much” finalized.

“I have given them approval to build a nuclear-powered submarine, rather than the old-fashioned, and far less nimble, diesel-powered submarines that they have now,” Trump said on Truth Social Thursday.