The United States on Saturday called for an immediate end to China's intensifying reclamation works in the South China Sea and vowed to continue sending military aircraft and ships to the tense region.
US Defense Secretary Ashton Carter told a high-level security conference in Singapore that Beijing was behaving "out of step" with international norms.
"First, we want a peaceful resolution of all disputes. To that end, there should be an immediate and lasting halt to land reclamation by all claimants," Carter said at the annual Shangri-La Dialogue on security with a high-level Chinese military delegation in the audience.
"We also oppose any further militarization of disputed features," he said.
He acknowledged that other claimants have developed outposts of differing scope and degree, including Vietnam with 48, the Philippines with eight, Malaysia with five and Taiwan with one.
"Yet, one country has gone much farther and much faster than any other.
"China has reclaimed over 2,000 acres, more than all other claimants combined and more than in the entire history of the region. And China did so in only the last 18 months," Carter said.
"It is unclear how much farther China will go. That is why this stretch of water has become the source of tension in the region and front-page news around the world."
Chinese actions 'reasonable and justified'
During a question and answer session after Carter's speech, a Chinese military official said the criticism was "groundless and not constructive".
"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 from China's Academy of Military Science.
Chinese delegation head Admiral Sun Jianguo, deputy chief of the general staff department at the People's Liberation Army, is scheduled to address the forum on Sunday.
Sun and Carter spoke cordially on the sidelines before a luncheon at the forum, an AFP photographer said.
"Freedom of navigation should be for the benefits of economic development, rather than sending military aircraft and vessels everywhere," said director of Foreign Affairs Office of China's National Defense Ministry Rear Admiral Guan Youfei in response to Carter's comments, according to China's state news agency Xinhua.
While in an interview released over the weekend by the Wall Street Journal, China's ambassador to the United States, Cui Tiankai, questioned the US's actions, saying "what the US is doing has given rise to a lot of questions in China."
Last week the Chinese military ordered a US Navy P-8 Poseidon surveillance aircraft to leave an area above the heavily disputed Spratly Islands. But the American plane ignored the demand.
Sun Jianguo (L) from the Chinese People's Liberation Army Navy, chats with US Secretary of Defense Ashton Carter (R) during the ministerial luncheon at the 14th Asia Security Summit, the International Institute for Strategic Studies (IISS) Shangri-La Dialogue 2015 in Singapore on May 30, 2015. Photo: AFP/Roslan Rahman
"There should be no mistake: the United States will fly, sail, and operate wherever international law allows, as US forces do all around the world," Carter said in Singapore.
"After all, turning an underwater rock into an airfield simply does not afford the rights of sovereignty or permit restrictions on international air or maritime transit."
China insists it has sovereignty over nearly all of the South China Sea, a major global shipping route believed to be home to oil and gas reserves.
Code of conduct
In his speech, Carter urged China and the 10-member Association of Southeast Asian Nations to adopt a "code of conduct" in the disputed waters this year.
ASEAN members the Philippines, Vietnam, Malaysia and Brunei claim parts of the sea, along with Taiwan.
In a speech at the forum, Malaysian defense minister Hishammuddin Hussein said if claimant countries did not exercise restraint, the territorial dispute "could escalate into one of the deadliest conflicts of our time, if not history".
Washington on Friday accused China of deploying two artillery pieces on one of its artificial islands in the South China Sea.
The heavy weapons, since removed, posed no security threat but their positioning -- within range of territory claimed by Vietnam -- underscored Washington's concerns that China is pursuing a massive island-building project for military purposes, US officials said.
Carter said in Singapore that his country "will support the right of claimants to pursue international legal arbitration and other peaceful means to resolve these disputes".
The Philippines infuriated China when it filed a formal complaint to the Permanent Court of Arbitration at The Hague in March 2014. China has so far refused to recognize the process.