A unit of China’s CRRC Corp, the world’s biggest train maker by revenue, on Thursday joined a group of its domestic peers in agreeing a deal to help build a high-speed link from Las Vegas to Los Angeles, underlining the rail giant’s lofty overseas ambitions. Announced in a joint statement by the Chinese firms and U.S. partner XpressWest at a government forum in Beijing, the deal is the latest in a series of deeper Sino-American business ties to be unveiled before President Xi Jinping visits the United States next week.