The prime minister said the region's traditional American-dominated system of "hub and spokes" relations, with the US at the centre and its allies on spokes radiating outwards, would remain but was no longer sufficient.

"We've had hub and spokes for a long time, and that shouldn't change," Mr Turnbull said. But the region needed a new "mesh" of strategic relations, he said, a close-knit structure where like-minded nations worked directly with each each other rather than through Washington.

"In the same way we've done with counter-terrorism," he told Fairfax Media on the weekend, elaborating on his keynote speech to Asia's main security conference, the Shangri-la Dialogue in Singapore.

This "mesh" model should now be applied to strategic affairs, he said, the conduct of long-term relations between nations.

China's assertiveness was one dominant concern among delegates to the dialogue, and US unreliability was another.

Without naming either country, Mr Turnbull referred to both in his speech. He criticised China's conduct in the South China Sea by condemning "unilateral actions to seize or create territory or militarise disputed areas".

And he addressed the global crisis of trust in the US under President Donald Trump by saying: "In this brave new world we cannot rely on great powers to safeguard our interests. We have to take responsibility for our own security and prosperity."

In a line in the prepared text of his speech but one that he omitted to deliver, the prime minister said the region needed to "find new sources of leadership to help the US shape our common good".

He said that "we are stronger when sharing the burden of collective leadership with trusted partners and friends". He didn't explicitly name any new sources of leadership, but already Australia has expanded its defence ties with Japan and Singapore, and Mr Turnbull gave great play to the potential of ASEAN, the 10-country Association of South-East Asian Nations.

"Our interests will not align on every issue - but we have to find a unity of purpose," he said.

The US Defence Secretary, James Mattis, who was present for the speech, later commended the Australian leader for "a good dose of Aussie pragmatic optimism".

Malaysian Defence Minister Hishammuddin Hussein told Bloomberg: "This needed to be said. Very pragmatic."

While most news reporting focused on Mr Turnbull's criticisms of China, an Australian analyst, Allan Gyngell, said that "the US stuff was more interesting for what was not said, and what was said about Australian responses".

The speech did not contain the standard fulsome effusions over the centrality of Australia's US alliance, obligatory for all prime ministers in recent decades.

This is despite the fact that two US cabinet secretaries, Mr Mattis and Secretary of State Rex Tillerson, are in Sydney on Monday for annual AUSMIN consultations.

And Mr Gyngell pointed to Mr Turnbull's statement that the US alliance "has never been a straitjacket for Australian policy-making". On one level this was unexceptional, he said, "but the fact that he chose to put it in was also interesting". It signalled that Australia was not constrained in going beyond the US alliance.

Mr Gyngell, former head of the Office of National Assessments and author of a new book on Australian foreign policy, Fear of Abandonment, said Mr Turnbull's pursuit of a "mesh" of relations beyond the "hub and spokes" was a "sensible way of proceeding in the face of all the uncertainty in the region and the world".

As prime minister in 1993, Paul Keating was critical of US preferences for a "hub and spokes" system of relations.

Mr Gyngell, a former Keating adviser, said that "Paul's view and my view is that great powers always like hub and spokes rather than multilateral arrangements because it gives them more power. The US was initially reluctant to multilateralise through the APEC [Asia-Pacific Economic Co-operation] leaders meetings and so on."

Mr Turnbull's call to multilateralise strategic relations - through a "mesh" of relations - was "consistent with Australian policy going back at least that far", he said.