Subs to help counter Chinese dominance: ex-US navy boss

A former US navy boss says Australia's acquisition of nuclear-powered submarines will help protect trade routes and undersea communication cables against Chinese aggression. 

Australia will spend up to $368 billion acquiring eight nuclear-powered submarines over the next three decades through the AUKUS pact, which includes the United States and UK.

Former US Navy secretary Richard Spencer says western nations need a presence in the area to deter a possible attack. 

"If China wants to make a play for power dominance - look at what they're doing already with cutting of the cables in Taiwan - you have to be able to show that you're in the area," he told the National Press Club on Monday.

"There's a great phrase, 'peace through presence'. I call it 'power through deterrence'. You have to be on the beat, you have to be on the patrol."

Mr Spencer said collective governments also needed to work with the private sector to ensure the success of the AUKUS pact, with includes technology collaboration in areas such as artificial intelligence and quantum.

He spoke of the build up US industry experienced during World War II as a precedent, with Henry Ford scaling up investment in his manufacturing line to be able to produce a B-24 aircraft every hour at its height.

"I use it as an example of how to focus government and private practice together to get the outcomes we need," he said.

"It's time we get back in shape and back to the weight room. We don't have the luxury of time in my eyes."

The former secretary also echoed the point made by the Australian defence minister, that the acquisition of nuclear submarines wasn't just about a potential war.

He said that trade and economic ties beyond military investment would help boost regional security.

"The subs are today's headlines and the first steps, but there is more," Mr Spencer said.

"The military is just one arrow in our quiver. There's one more powerful arrow in the quiver and that's commerce."

Defence Minister Richard Marles said the purchase of three nuclear submarines from Washington before a new AUKUS class submarine is constructed and acquired wasn't tied to any war pact with the White House.

"Yes, nuclear-powered submarines have obviously the capacity to operate in the context of war, but the primary intent here is to make our contribution to the stability of the region," he said. 

"What Australia would do or not do in respect of any future conflict will be a matter to be considered at that time by the government of the day."

Mr Spencer said while he would hope Australia was beside the US in any war, it would be a decision made by Canberra at the time.