As discussions continue over when and where a summit between U.S. President Donald Trump and North Korean leader Kim Jong Un will take place, Japan's former chief negotiator for multilateral talks aimed at ending the North's nuclear program on Tuesday warned that the current U.S. administration has virtually no expertise on Pyongyang.

"Almost nobody in the Trump administration has much knowledge about North Korea," Mitoji Yabunaka, a professor at Kyoto's Ritsumeikan University, said at a speech in Kyoto.

Referring to John Bolton, the hawkish former U.N. ambassador who took over Monday as Trump's national security adviser, Yabunaka said he "comes across as more of a television commentator, and there is a shortage of North Korean experts in the State Department."