Since taking office in a snap election in June, the liberal Lee has taken steps to lower tensions with the nuclear-armed North, and the issue is one where he is expected to find common ground with Trump, who still boasts of his historic summits with North Korean leader Kim Jong Un.

North Korea is stepping up criticism of South Korea's new President Lee Jae Myung as he prepares for his first summit with U.S President Donald Trump, calling Lee's efforts to engage with Pyongyang a "pipedream".