China’s newest nuclear-powered submarine sank pierside in the spring and the Chinese Navy tried to conceal the loss, according to two US defense officials.

Building a potent nuclear submarine force would help China tighten control over its peripheral waters and improve its ability to seize Taiwan.

China’s newest nuclear attack submarine has sunk in a shipyard accident, in a setback to the country’s attempts to overtake the United States in a naval arms race, according to US officials.