BEIJING—China's Defense Ministry said its first aircraft carrier would be used for "research, experiments and training" and would not affect its defensive naval strategy, in an apparent attempt to ease regional concerns that the vessel could be used to enforce Chinese territorial claims.

Senior Col. Geng Yansheng, a Defense Ministry spokesman, also confirmed for the first time that Chinese pilots were training to operate from the carrier, which is based on an empty hull bought from Ukraine, and which is due to start sea trials...