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."
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 criticize 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."
Carter is currently on an 11-day trip to Asia, his second since becoming the U.S. defense secretary earlier this year. With an eye on Chinese activity in the South China Sea, he has made maritime security a theme of his travels.
In a speech at Pearl Harbor in Hawaii, he called for an immediate end to land reclamation by all parties claiming parts or all of the South China Sea and a halt to militarization of the islands.
The U.S. defense chief said competing claims of sovereignty over the resource-rich islands of the South China Sea could not be solved militarily, and he insisted U.S. forces would continue to "fly, sail and operate" in the region to ensure the freedom of navigation and overflight permitted by law.
"America, alongside its allies and partners ... will not be deterred from exercising these rights...," Carter said. "Turning an underwater rock into an airfield simply does not afford the rights of sovereignty or permit restrictions on international air or maritime transit."
The Pentagon chief called for a renewed diplomatic effort to resolve the competing sovereignty claims to the resource-rich islands, with the Association of South East Asian Nations (ASEAN) taking a lead because of its central role in the region's security architecture.
"Right now, at this critical juncture, is the time for renewed diplomacy, focused on a finding a lasting solution that protects the rights and interests of all," Carter said.