Days before Chinese President Xi Jinping made a high-profile visit to the United States last week, Beijing said six Chinese businesses would join forces with a U.S. company to build a high-speed rail link between Los Angeles and Las Vegas.

The news was a double whammy for Japan, as it followed a decision by Indonesia to drop a project to build its first high-speed train line. Jakarta rejected offers from the only bidders, Japan and China.

China's U.S. announcement has raised alarm in Japan's railway industry, which plans to bid for the construction of a West Coast link from Los Angeles to San Francisco. There is now the possibility that a Chinese group could outmaneuver a Japanese bid — in a replay of a tender to supply railcars for the Boston subway last year.