Russian President Vladimir Putin welcomes North Korea's leader Kim Jong Un during their meeting in Vladivostok, Russia, April 25, 2019. Kim Jong Un met Russian President Vladimir Putin on Thursday at a summit designed to show that Washington is not the only power able to set the agenda on Pyongyang's nuclear programme. Alexander Zemlianichenko/Pool via REUTERS

North Korea's leader Kim Jong Un walks to meet with Russian President Vladimir Putin in Vladivostok, Russia, April 25, 2019. The two men embarked on a day of talks on an island off the Russian Pacific city of Vladivostok two months after Kim's summit with U.S. President Donald Trump ended in disagreement, cooling hopes of a breakthrough in the decades-old nuclear row. Alexander Zemlianichenko/Pool via REUTERS

Russian President Vladimir Putin and North Korea's leader Kim Jong Un shake hands during their meeting in Vladivostok, Russia, April 25, 2019. Putin and Kim, in their first ever face-to-face encounter, smiled broadly and shook hands outside the summit venue, a university campus. They then stood side by side on an escalator, chatting with help from interpreters, as they made their way to an upper floor to begin their talks. Alexander Zemlianichenko/Pool via REUTERS

Russian President Vladimir Putin and North Korea's leader Kim Jong Un smile while posing for a photo prior to their talks in Vladivostok, Russia, Thursday, April 25, 2019. Kim Jong Un met Russian President Vladimir Putin on Thursday at a summit designed to show that Washington is not the only power able to set the agenda on Pyongyang's nuclear programme. Alexander Zemlianichenko/Pool via REUTERS

Russia's President Vladimir Putin shakes hands with North Korea leader Kim Jong Un at the Far Eastern Federal University campus at Russky Island in the far eastern city of Vladivostok, Russia April 25, 2019. The two men embarked on a day of talks on an island off the Russian Pacific city of Vladivostok two months after Kim's summit with U.S. President Donald Trump ended in disagreement, cooling hopes of a breakthrough in the decades-old nuclear row. REUTERS/Shamil Zhumatov

Russian President Vladimir Putin welcomes North Korea's leader Kim Jong Un for the talks in Vladivostok, Russia April 25, 2019. Putin and Kim, in their first ever face-to-face encounter, smiled broadly and shook hands outside the summit venue, a university campus. They then stood side by side on an escalator, chatting with help from interpreters, as they made their way to an upper floor to begin their talks. Alexander Zemlianichenko/Pool via REUTERS