The South China Sea has become a growing source of tension between China and the US (AFP Photo/Ted Aljibe) Two Chinese fighters have conducted an "unsafe" intercept of a US spy plane in international air space over the South China Sea, the Pentagon said, as tensions mount in the strategically vital waters. Tensions between China and the United States are high in the disputed waterway, an important shipping route thought to be home to vast energy deposits, and which Beijing claims almost in its entirety. "The Department of Defense (DoD) is reviewing a May 17 intercept of a US maritime patrol reconnaissance aircraft by two tactical aircraft from the People's Republic of China (PRC)," Pentagon spokesman Major Jamie Davis said in a statement Wednesday.