PEARL HARBOR, Hawaii — When the U.S. wanted to show the world it didn’t recognize what it called China’s “excessive” territorial claims in disputed waters of the South China Sea this fall, it sent a warship near one of Beijing’s newly built artificial reefs.

The move came amid a debate about whether the U.S. has enough ships to meet challenges posed by a fast-growing, increasingly assertive Chinese navy that is unsettling some of its neighbors. In its latest move, China announced last week that it would build its second aircraft carrier, this one with domestic technology.

The Navy and its regional component, the U.S. Pacific Fleet, both have fewer ships now than in the mid-1990s. Navy officials said vastly improved technology on those vessels outweighs any disadvantage from a drop in numbers.

Questions about whether the Pacific Fleet has enough resources are more of a reflection of regional anxieties than the Navy’s actual capability, said its commander, Adm. Scott Swift.