China has rejected U.S. allegations that it is using vague territorial claims unsupported by international law to gradually assert control in the disputed South China Sea.

Foreign Ministry spokesman Hong Lei is urging the U.S. to take a "rational and fair attitude." He said Saturday that playing up tensions is not conducive to maintaining peace and stability.

According to him, China has been committed to resolving maritime disputes directly with its neighbors.

The United States said Wednesday that actions by China have raised concerns it was trying to assert control over an area covering roughly 80 percent of the South China Sea based on Chinese maps despite the objections of its neighbors.