China's new reclaimed islands in South China Sea 'causing concern', says US admiral

China's creation of more than 4 sq km of artificial islands in the South China Sea is increasing tensions with the US and its allies, according to Pacific Fleet Commander Harry Harris.

"What's drawing a lot of concern … is the unprecedented land reclamation … by China," Admiral Harris said in Canberra yesterday. "China is building artificial land by pumping sand onto live coral reefs … and paving over them with concrete."

China, alongside a number of Southeast Asian nations, contests parts of the waters that house some of the world's busiest shipping lanes. The Philippines has accused China of undertaking large-scale reclamation work on contested reefs.

Disputes over the sea, with China claiming about 80 per cent under a nine-dash line drawn on a 1940s map, have escalated as the nation expands its military's reach to back its territorial interests and challenges decades of US Navy dominance in the Pacific. The tensions risk overshadowing trade and investment ties with Southeast Asia.

The United States urged all claimants to comply with the 2002 Declaration of Conduct between China and the Association of Southeast Asian Nations, in which the parties committed to "exercise self-restraint in … activities that would complicate or escalate disputes and affect peace and stability", Harris said. "How China proceeds will be a key indicator of whether the region is heading towards confrontation or cooperation."

China's reclamation work in the South China Sea might create inhabited islands that declare allegiance to Beijing, bringing its military ever closer to the Philippines, President Benigno Aquino said last week. If the reefs were built up enough, "somebody might say 'we're a new country'".