BEIJING—China officially welcomed its first aircraft carrier to its navy, offering a public display of its ambitions to challenge U.S. naval supremacy in Asia in the midst of a territorial dispute with Japan that has inflamed nationalism at home.

The carrier, christened the Liaoning after China's northeastern province, is at least several years away from minimal combat readiness, military experts say. In particular, Chinese fighter pilots are still learning skills needed for taking off and landing on a moving deck. Diplomats...