US President Joe Biden called on China’s leader Xi Jinping to play a mediating role in the conflict with North Korea on Monday after the two met on the Indonesian resort island of Bali. “I made it clear to President Xi Jinping that I thought they had an obligation to attempt to make it clear to North Korea that they should not engage in long range nuclear tests,” Biden said. If North Korea did, he said, the Americans would have to take defensive actions on behalf of themselves and their allies. The situation is tense because of repeated North Korean missile tests and the looming threat of a po…