SEOUL: Chinese President Xi Jinping is set to arrive in North Korea on Monday after hosting back-to-back summits with US President Donald Trump and Russia's Vladimir Putin last month. China, Washington's chief geopolitical rival, has been North Korea's main trading partner by far for decades and a key source of diplomatic and economic support for the country of around 26 million people. Xi's visit comes as North Korea's nuclear talks with Washington remain deadlocked. The White House said last month that Xi and Trump "confirmed their shared goal to denuclearize North Korea" during their summit in Beijing. Chinese foreign ministry…