South Korea's Foreign Minister Ban Ki-moon was set to arrive in Japan on Sunday for talks with Japanese leaders on North Korea and other issues.
Ban, the next UN secretary-general, was scheduled to meet his Japanese counterpart Taro Aso on Sunday evening, Japan's Foreign Ministry said.
The two are expected to talk about coordinating U.N. Security Council sanctions imposed on North Korea after its nuclear test, and to discuss resuming stalled international talks on the North's nuclear ambitions.
Ban was also expected to meet Prime Minister Shinzo Abe on Monday.
Pyongyang lashed out at Japan on Saturday, demanding that Tokyo stay away from the negotiations and calling Japanese officials "political imbeciles" for saying they will not accept a nuclear North Korea.