SINGAPORE - US Defense Secretary Ash Carter said on Saturday that Beijing's island-building in the South China Sea was undermining security in the Asia-Pacific but, despite his blunt remarks, the response from Chinese officials was measured.
Carter, speaking to top defence officials from the Asia-Pacific at the annual Shangri-La Dialogue in Singapore, 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."
However, he added: "We all know there is no military solution to the South China Sea disputes. Right now is the time for renewed diplomacy, focussed on a finding a lasting solution that protects the rights and interests of all."
A Chinese military delegate to the forum said Carter was wrong to criticize China, but his comments were not as hostile as those made at the Shangri-La Dialogue in past years.
"This year, Carter's speech is more balanced...It's helpful for building new ties between China and the US as major powers, and also helpful to improving military relationships," Senior Colonel Zhao Xiaozhuo of China's Academy of Military Science told reporters on the sidelines of the forum.
Bonnie Glaser, of the Center for International Strategic Studies, said both China and the United States were trying to tone down the rhetoric after angry exchanges at the event last year.
"Carter's trying not to be too harshly targeting of China but at the end of the day the real problem is China and everyone knows that," she said.
The official Chinese response will only come on Sunday when Admiral Sun Jianguo, the head of Beijing's delegation, addresses the conference.
China also took a measured tone after bilateral meetings with Japan and Vietnam on Friday, two of the states it is embroiled with in maritime sovereignty disputes.
Sun said after a meeting with Vietnam's deputy defence minister General Nguyen Chi Vinh that he believed the two could solve the South China Sea dispute through mutual co-operation.
A joint agreement between Japan and China on a "maritime and air liaison mechanism" - a hotline aimed at preventing conflicts escalating at sea - can hopefully be signed at an "early date", China's defence ministry said after Sun met Japan's Director-General of the Ministry of Defense, Hideshi Tokuchi.
China, Malaysia, Taiwan, Brunei, Vietnam and the Philippines have overlapping claims in the resource-rich South China Sea.
Japan and China both claim islands that lie between them in the East China Sea.
Earlier this week, Beijing was assertive about the disputes.
In a policy document issued by the State Council, the country's cabinet, China vowed to increase its "open seas protection", switching from air defence to both offence and defence, and criticized neighbours who took "provocative actions" on its reefs and islands.
Carter's remarks in Singapore 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.
The US defence chief insisted US 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."
Japan's defence minister said China and other parties in the dispute had to behave responsibly.
"If we leave any unlawful situation unattended, order will soon turn to disorder, and peace and stability will collapse," Gen Nakatani told the forum. "I hope and expect all the countries, including China, to behave as a responsible power," he said.
Malaysia's defence minister, Hishammuddin Hussein, urged all parties in the South China Sea dispute to exercise restraint or face potentially dangerous consequences.
"This has the potential to escalate into one of the deadliest conflicts of our time, if not history," he said.
"Inflamed rhetoric does not do any nation any good".