Singapore - While rival claims over the South China Sea fishing grounds and shipping lanes go back centuries, China's intensifying land reclamation and island-building in the Spratly archipelago and other contested waters is an escalating global dispute.

China laid out its ambitions for a bigger naval presence far from its coasts last week, prompting concerns that Beijing will back up its claims to new territories by flexing its military muscle in one of the world's most strategic waterways.

Critics from around the world attending Asia's top defence summit over the weekend accused China of setting a confrontational tone, undermining security in the Asia-Pacific, and hurting diplomatic efforts to resolve competing claims from Vietnam, the Philippines, and other nations surrounding the resource-rich sea.

"The United States is deeply concerned about the pace and scope of land reclamation in the South China Sea, the prospect of further militarisation, as well as the potential for these activities to increase the risk of miscalculation or conflict among claimant states," said US Defence Secretary Ashton Carter, speaking on Saturday at the three-day Shangri-La Dialogue, in Singapore.

 US condemns China's land reclamation

"Turning an underwater rock into an airfield simply does not afford the rights of sovereignty or permit restrictions on international air or maritime transit," Carter said.

Beijing claims sovereignty of about 90 percent of the South China Sea - despite overlapping claims from the Philippines, Vietnam, Malaysia, Taiwan, and Brunei.

That claim could be strengthened by China's rapidly expanding campaign to construct artificial islands atop partially submerged reefs. The US estimates some 800 hectares of dry land have been created in the last 18 months, an amount Washington expects will continue to grow.

How far will China go?

Carter called for an immediate halt to land reclamation in the South China Sea by China and other countries, which Beijing promptly rejected. Carter pledged to maintain the US presence with warships and aircraft conducting military operations in what Washington considers international airspace and waters.

"It is unclear how much farther China will go," he said. "That is why this stretch of water has become the source of tension in the region and front-page news around the world."

Carter's remarks followed the disclosure by the Pentagon that China had put mobile artillery at one of its reclaimed islands in the South China Sea.

While remaining neutral in the increasingly heated dispute, Singapore Prime Minister Lee Hsien Loong, also speaking at the defence summit, said the current course of escalating tensions is unsustainable.

"Actions provoke reactions," Lee said. "The US is responding to Chinese activities with increased over-flights and sailings near the disputed territories to signal that it will not accept unilateral assertions of sovereignty in the South China Sea.

"These maritime disputes are … most unlikely to be solved anytime soon. But they can and should be managed and contained. If the present dynamic continues, it must lead to more tensions and bad outcomes."

Other countries expressing concern over China's land reclamation included Malaysia, whose defence minister, Hishammuddin Hussein, called for cool heads and adherence to the rule of law.

"If we are not careful it would escalate into one of the deadliest conflicts of our time, if not our history," Hishammuddin said. "Just because a region appears to be peaceful and prosperous doesn't mean the prospects of conflict do not arise."

Improving humanitarian conditions

China's formal response to the delegates rejected criticism over its island-building and maintained it was exercising its sovereignty.

Chinese dredging vessels purportedly seen near the disputed Spratly Islands Reuters]

Admiral Sun Jianguo, vice-chief of staff of the People's Liberation Army who led the Chinese delegation, told delegates on Sunday morning that China is developing islands in the South China Sea largely to enhance its ability to assist humanitarian efforts, maritime search and research, disaster relief, and global security.

"China has carried out construction on some islands and reefs in the South China Sea mainly for the purpose of improving the functions of the relevant islands and reefs, and the working and living conditions of personnel stationed there," Sun said.

Following his formal remarks, multiple delegates pressed Sun for assurances over China's intentions in the South China Sea. Sun protested that too much was being made of the issue.

"There is no reason for people to play up this issue in the South China Sea," he said.

The admiral's appeals for dialogue and negotiation over territorial disputes contrast with earlier language accusing the US and other countries of meddling into its affairs.

China's Xinhua news agency said some summit participants "attempt to monopolise the right to speak in the field of international security… They echo each other, distort the truth, magnify differences, add fuel to fire, so that dialogue diverges from the path of strengthening exchanges and enhancing mutual trust".

The Global Times, a Chinese government-run newspaper, warned last week:

"If the United States' bottom line is that China has to halt its activities, then a US-China war is inevitable in the South China Sea."

China's new maritime outposts create the potential for military uses, although China denies having military aspirations for its newly minted islands. Chinese-built structures that appear on satellite images include radar facilities and a runway capable of handling aircraft.

Beijing maintains it has the right to conduct land reclamation - as have Vietnam, the Philippines, and Malaysia to a far lesser extent - and maintains the artificial islands will be used for humanitarian, environmental, fishing and other purposes.

US reconnaissance

 Philippines and China tussle over South China Sea territory

American officials have expressed concern that China's activities will lead to the enforcement of a possible air defence identification zone over the South China Sea, similar to one it declared over disputed Japanese-held islands in the East China Sea in 2013.

Speaking on the sidelines of the defence summit, Senator John McCain, chairman of the Senate's armed services committee, said US forces must continue entering what he called international waters and airspace in the tense region, and said the US should not recognise a 12-nautical mile zone - considered a restricted area under international convention - surrounding the man-made islands.

"There is no 12-mile barrier around these reclaimed lands, there absolutely is not. To respect that would sort of be a de facto recognition of what the Chinese are trying to achieve in these reclaimed lands," McCain told Al Jazeera.

Last week, the US navy sent a P-8 reconnaissance plane carrying navy and television camera crews to film Chinese island-building activity in the Spratly Islands, prompting warnings by a Chinese navy radio operator to leave the area. The warnings went unheeded, US officials said.

A Pentagon report released in early May on China's military power warned while the intent of Beijing's construction in contested islands in the South China Sea is unclear, five emerging outposts could be used for surveillance systems, harbours, airfields, and logistical support.

Meanwhile, the Philippines is challenging China at a UN tribunal, claiming its so-called "nine-dash line" - from a 1947 map that China uses as the basis to claim sovereignty over most of the South China Sea - is legally invalid.

China refuses to participate in the arbitration.

Follow Tom Benner on Twitter: @tgbenner

Source: Al Jazeera