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".

SEOUL, South Korea (AP) — South Korea’s new President Lee Jae Myung will travel to Washington later this month to meet with U.S. President Donald Trump, Lee’s office said Tuesday, for talks on trade and defense cooperation in the face of nuclear-armed North Korea and other threats.

South Korean President Lee Jae Myung pledged to "respect" North Korea's political system and said Seoul would not seek unilateral reunification in a speech to mark Liberation Day.