SINGAPORE —  US Defense Secretary Ash Carter's opening speech at the 15th annual Asia Security Summit was clear: China's activities are spurring newfound tensions and unrest in the Asia-Pacific region.

"In all of our interactions with our Chinese counterparts, the United States consistently encourages China to take actions that uphold – and do not undercut – the shared principles that have served so many in Asia-Pacific so well."

Commonly referred to as the Shangri-La Dialogue, run by the London-based International Institute for Strategic Studies (IISS), the annual three-day summit has become an unofficial conclave for regional defense ministers, along with European and US military officials, to openly discuss and debate security matters.

Carter said that China's activities in the South China Sea, cyberspace, and regional airspace, have created growing anxiety in the region. "Indeed, in the South China Sea, China has taken some expansive and unprecedented actions, that have generated concerns about China's strategic intentions."

The result is that countries in the region have been taking action publicly and privately, at the highest levels, to voice concerns. "As a result, China's actions in the South China Sea are isolating it, at a time when the entire region is coming together and networking, Carter said. "Unfortunately, if these actions continue, China could end up erecting a Great Wall of self-isolation."

Carter emphasized the right of the international community to exercise the freedom of navigation and overflight, and peaceful resolution of disputes in accordance of international law.

Carter discussed the challenges by the Philippines to China's claims to most of the South China Sea, roughly the size of India. A ruling by the United Nations Permanent Court of Arbitration at The Hague is expected by the end of the summer. Carter said that this was an opportunity for China to "recommit to a principled future, to renewed diplomacy, and to lowering tensions, rather than raising them." China has already stated it does not recognize the court's jurisdiction.

Jia Qingguo, dean of the School of International Studies at Peking University, challenged Carter's comments on Chinese activities in the South China Sea. Jia is also a member of the Standing Committee and the Foreign Affairs Committee of the National Committee of the Chinese People's Political Consultative Conference, which is a powerful political advisory body for the Communist Party.

"I just think that the dispute between China and the US over the South China Sea has been overblown," he said. "It is only part of the relationship between our two countries, which is huge, vast and complicated."  Further, "the artificial islands China builds, I think a lot of countries have engaged in this kind of practice, including Vietnam, Philippines, Japan, and South Korea; so why focus on China? What's the difference between China and the US over the freedom of navigation on the high seas? I think both China and the US are committed to this principle."

Carter said that the US stands for the principle of rule of law and abiding by international law in the commons, which means freedom of navigation in the sea and the air. The US does not take a position on the dispute over sovereignty in the South China Sea, but does reserve the right to exercise the right to transit areas of international waters and airspace.

"The reason that people are focusing on China this year is because China is doing by far and away more of this kind of [land] reclamation and militarization than any other party [in the South China Sea]," Carter said. "That is the reason why parties in the region that are concerned about principle are focusing on China. It is China's actions."

"These actions…are destabilizing and self-isolating," Carter added.

According to the new IISS report, Asia-Pacific Regional Security Assessment, released during the summit, China now occupies six reefs and shoals in the South China Sea with many of them showing signs of militarization with barracks, enlarged harbors, lengthy runways, early warning radar, and anti-aircraft placements. China had assured the US during meetings between US President Barack Obama and Chinese President Xi Jinping that China would not militarize the islands. Despite these assurances, China fielded J-11 and JH-7 combat aircraft, along with HQ-9 surface-to-air missile batteries, on Woody Island in the Paracels. There were also unconfirmed reports that China installed YJ-62 anti-ship missiles around the Paracels, said the report.

This activity is of great concern to the region, said the report. Oil and gas shipments from the Middle East travel directly through the area on their way to Japan, South Korea, the Philippines, and Taiwan. The report indicated that $5.3 trillion in commerce travels through the South China Sea annually. Fears of a Chinese sea blockade of oil and gas to the region could serve as economic, political and military coercion.