China has made several moves in recent months to advance its ambitious aim to become the trade and transportation hub of Asia.To its west, China has agreed to build a rail line across Central Asia.... Beijing also said it would help Vietnam plan three rail lines leading to the countries’ shared border.... The nation’s top leader, Xi Jinping, will need close cooperation from border countries, some of which are politically volatile, like Kyrgyzstan, or internationally isolated, like North Korea.