The Republic of Korea and Japan offered muted reactions on Monday to Donald Trump's suggestion that, as president, he would withdraw troops from both countries and allow them to develop their own nuclear arsenal.

There are nearly 30,000 US troops permanently stationed in the ROK and 47,000 in Japan, with little appetite for nuclear weapons in either nation.

Asked to respond to Trump's 'America first' policy to wean nations off US support, ROK Defense Ministry spokesman Moon Sang-gyun said it would be inappropriate to comment on remarks by a US presidential candidate.