Japan is among the four nations on US President Barack Obama's Asia tour itinary
China's role in stopping North Korea from forging ahead with a nuclear weapons programme is "critically important", US President Barack Obama told reporters in Japan on Thursday as he issued a stern ticking off to Pyongyang.
"North Korea has engaged in provocative actions for the last several decades. It's been an irresponsible actor on the international stage for the last several decades," he said.
"They are the most isolated country in the world. They are subject to more international sanctions and international condemnation than any country in the world.
"Working with Japan, working with the Republic of Korea and working with China, we can continue to apply more and more pressure on North Korea so that at some junction, they end up taking a different course. China's participation in pushing the DPRK (North Korea) in a different direction is critically important," he said.