U.S. Defense Secretary Ash Carter warned on Saturday that Beijing's island-building in the South China Sea was undermining security in the Asia-Pacific and he called for a diplomatic push to solve the territorial dispute that is driving China's effort.
Carter, speaking to top defense officials from across the Asia-Pacific, acknowledged that several countries had created outposts in the region's disputed islands, but he said the scope of China's activity created uncertainty about its future plans.
"China has reclaimed over 2,000 acres, more than all other claimants combined ... and China did so in only the last 18 months," Carter told the Shangri-La Dialogue security forum. "It is unclear how much farther China will go."
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He said the United States was "deeply concerned" about the scale of China's land reclamation and the prospect of further militarization of the islands, saying it would boost "the risk of miscalculation or conflict."
A Chinese military delegate to the forum said the remarks were uncalled for.
"The freedom of navigation in the South China Sea is not at all an issue because the freedom has never been affected," said Senior Colonel Zhao Xiaozhuo of China's Academy of Military Science.
"It is wrong to criticise China for affecting peace and stability through construction activities."
Carter's remarks came a day after the Pentagon confirmed reports that China had put mobile artillery at one of its reclaimed islands in the South China Sea, a move that Republican Senator John McCain said was "disturbing and escalatory."