The much-anticipated speech by US Secretary of Defense Ashton Carter to the Shangri-La Dialogue in Singapore today struck an intelligent note of US determination regarding security in the South China Sea, without being needlessly confrontational. The full text has just gone online here.

There's been a drumbeat of media speculation in recent days that the scene was being set for an exceptionally tense weekend here at this gathering of ministers, senior officials and experts from across the Indo-Pacific and beyond. Attention has focused on China's extraordinary acceleration of island-building in contested waters in the South China Sea, as well as growing signs of resolve from the US and others in challenging this form of provocation.

In what seemed a sign of things to come, a few days ago Carter included a firm indication of American resolve in a speech in Hawaii that was otherwise about a changing of the guard in Pacific Command and Pacific Fleet. It wasn't an ultimatum, but the clearest yet expression of where the US stands on the Chinese island-building and the right of all countries to fly or sail their forces freely in international waters. US forces had earlier allowed a CNN television crew to join a surveillance flight in the vicinity of the artificial islands, where they witnessed Chinese forces warning the US flight to keep away from a 'military zone', behaviour that is reportedly becoming quite frequent.

This preview strategy is turning out to be a smart US move. It set the stage for Carter's Singapore speech in a way that allowed him to emphasise the reasonableness of the US approach.

To be sure, Carter still conveyed some strong messages. Without specifically speaking in terms of deterrence, he noted that the US would continue to make its best capabilities and newest military technologies part of its strategic footprint in Asia. He called for an end to island-building by all states in the South China Sea, and a halt to any further militarisation. Significantly, he affirmed:

...the United States will fly, sail, and operate wherever international law allows, as US forces do all over the world. America, alongside its allies and partners in the regional architecture, will not be deterred from exercising these rights...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.

This remains sensibly ambiguous about whether the US and its friends and allies would exercise that right within 12 nautical miles of the new artificial islands China has created, though it makes it plain that the US does not rule out such action.

But the Shangri La speech was less a ratcheting up of tensions than a narrative that put American expressions of determination on the South China Sea into a context that aligns American involvement with the interests of the wider region in stability and associated prosperity.

Thus, in language co-opting China's 'community of common destiny', Secretary Carter emphasised that a stable Asia would need to be one in which 'everyone rises, everyone wins'. He referred to India, Japan, and smaller powers whose rights and interests needed to be protected. He endorsed ASEAN-centric institutions such as the East Asia Summit and the ASEAN Defence Ministers Meeting Plus.

Above all, he made the point that China's actions were putting it out of step with the region, with global stakeholders in the security of the South China Sea, and with international rules and norms.

Last year's Shangri-La Dialogue involved a dramatic heightening of rhetoric from the Chinese delegation, which arguably turned out to be counter-productive for China's interests. Stark, confrontational language tomorrow from Admiral Sun Jianguo, China's delegation leader, would confirm Secretary Carter's point about China being out of step.

US-China diplomacy around the South China Sea and the Shangri-La Dialogue is becoming both subtle and serious. There are at least three simultaneous themes. First, the Americans and the Chinese are each looking to show resolve. Second, they are looking also for ways to restrain or limit any kind of clash — neither side actually wants an incident at sea or in the air to escalate. But third, they are also looking for that messaging edge which can demonstrate that the other side was the proximate cause of any confrontation.