World North Korean supreme leader Kim Jong Un spent his birthday in Beijing during a three-day trip that will likely include a summit alongside Chinese President Xi Jinping, with whom he’s shored up relations amid an unprecedented warming of ties between Pyongyang and Washington. Kim arrived Tuesday by armored train to the Chinese capital and was accompanied by an entourage that included his wife, Ri Sol Ju, as well as leading senior members of the young ruler’s inner cadre. The official Korean Central News Agency reported on Kim’s departure Monday, while Chinese officials confirmed that he had arrived on Tuesday at the behest of Xi, who also serves as head of the ruling Communist Party of China (CPC). “Chairman Kim Jong Un is visiting China at the invitation of General Secretary of the Central Committee of the CPC and President Xi Jinping,” Chinese Foreign Ministry spokesperson Lu Kang said Tuesday during a press briefing. “China and the DPRK are close neighbors,” he added, referring to North Korea’s official title, the Democratic People’s Republic of Korea. “It is an important part of our fine tradition to maintain high-level exchanges. As for the arrangements of Chairman Kim Jong Un’s visit, we will release relevant information in…