North Korean leader Kim Jong Un arrives at the railway station in the Russian far-eastern city of Vladivostok, Russia, April 24, 2019. Kim Jong Un arrived in the Russian city of Vladivostok on Wednesday for a summit he is likely to use to seek support from President Vladimir Putin while Pyongyang's nuclear talks with Washington are in limbo. REUTERS/Shamil Zhumatov

North Korean leader Kim Jong Un disembarks from a train during a welcoming ceremony at a railway station in the far eastern settlement of Khasan, Russia April 24, 2019. The armoured train carrying Kim -- on his first official visit to Russia -- pulled into the quayside station in Vladivostok, on the Pacific Ocean, a few hours after crossing from North Korea into Russia. Press Service of Administration of Primorsky Krai/Alexander Safronov/Handout via REUTERS

North Korean leader Kim Jong Un takes part in a welcoming ceremony at a railway station in Khasan, Russia in this undated photo released on April 24, 2019 by North Korea's Central News Agency (KCNA). After a brief delay while the door of Kim's carriage was lined up with a red carpet laid out on the platform, the door opened and a smiling Kim stepped out. Earlier, at a stop on the border, Kim told Russian state television he was hoping for useful and successful discussions with Putin. KCNA via REUTERS

North Korean leader Kim Jong Un attends a welcome ceremony as he arrives at the railway station in the Russian far-eastern city of Vladivostok, Russia, April 24, 2019. Kim will sit down for talks with Putin on Thursday at a university campus on an island just off Vladivostok. It will be the first summit between the two leaders, and the standoff over Pyongyang's nuclear programme will top the agenda, according to a Kremlin foreign policy aide. REUTERS/Shamil Zhumatov

North Korean leader Kim Jong Un arrives at the railway station in the Russian far-eastern city of Vladivostok, Russia, April 24, 2019. "I hope that we can discuss concrete questions about peace negotiations on the Korean peninsula, and our bilateral relations," he said through an interpreter. The meeting comes two months after a summit in Vietnam between Kim and U.S. President Donald Trump broke down over disagreement on ending the North's nuclear programme. REUTERS/Shamil Zhumatov

North Korean leader Kim Jong Un arrives in Vladivostok, Russia in this undated photo released on April 24, 2019 by North Korea's Central News Agency (KCNA). A North Korean official heavily involved in advancing the U.S.-North Korean talks, Kim Yong Chol, was removed from a top post, South Korea's Yonhap news agency reported. He had visited the White House in January to meet Trump. KCNA via REUTERS