Diplomatic assertion best on China, Carr

Tensions in the South China Sea are only warming up but Australia's options beyond a "vigorous diplomatic assertion" are limited, former foreign minster Bob Carr believes.

China has deployed anti-ship missiles, surface to air missiles and other military equipment on the disputed Spratly Islands and Woody Island.

Mr Carr says Senator Jim Molan's "brutally realistic" assessment last week that China had won in the South China Sea was backed publicly and privately by other senior military members.

"If you're reading the balance of power in the situation there are Australians in our military who would say that China's achieved its objectives," he told Sky News on Sunday morning.

"I don't see what options Australia's got beyond a vigorous diplomatic assertion and what options America has got beyond continuing freedom of navigation patrols perhaps on a more regular rotation than what's happening now."

Mr Carr supported comments made by Defence Minister Marise Payne overnight at the Shangri-La Dialogue, an annual defence and security summit.

"Nations must also have the right to be free from coercion or criticism when they lawfully and reasonably communicate concerns about the behaviour of others," she said.

Those words were in turn echoed by US Defense Secretary Jim Mattis who raised the prospect of further action by the US against China's militarisation of man made islands in the region.