The commander of the U.S. Pacific Fleet says China is using land reclamation to create "a great wall of sand" in disputed areas of the South China Sea, causing serious concerns about its territorial intentions.

Admiral Harry Harris Jr. told a naval conference in Australia on Tuesday that competing territorial claims by several nations are increasing regional tensions and the potential for miscalculations.

Harris said there is particular concern about what he called "unprecedented land reclamation currently being conducted by China" to buttress its territorial claims.

He said China "is creating a great wall of sand" with dredges and bulldozers over the course of months.

Harris said the rapid pace and scope of China's construction of man-made islands "raises serious questions about Chinese intentions."