Key US treaty should have 'assumptions' questioned

Australia should not assume its most important security alliance with the US will always exist or won't change, security experts say, as the two nations mark a major milestone.

Originally an agreement between Australia, New Zealand and the US, the ANZUS treaty on Tuesday reaches its 75th year.

The alliance was signed in 1951 to protect security in the Pacific, and was invoked for the first time by Australia in response to the September 11 terrorist attacks in 2001.

Security analyst and former naval officer Jennifer Parker described the US alliance as the "bedrock" of Australian security and strategic thinking.

"I don't think that we should always assume that the alliance will always be there or nothing will change," she told AAP.

Polling of Australian attitudes towards the US has shown a massive crash in confidence in the Trump administration, but a clear majority of survey participants still think the relationship with Washington is important for the nation's security.

"People are concerned about our changing strategic circumstances and the prospect of conflict in the region," Ms Parker said.

Australia and the US have stepped up their security ties, entering into the AUKUS pact alongside the UK, which will provide Australia with nuclear-powered submarines.

From 2027, the US and UK will be rotating nuclear-powered submarines out of HMAS Stirling in Western Australia.

Critics of the alliance with the US say it compromises Australia's independence and risks entanglement in conflicts abroad.

Australian Strategic Policy Institute Defence Strategy Program Director Mike Hughes said one of the reasons why the alliance has lasted is because it continues to meet the needs of both partners.

"It is something that is sought explicitly by both the United States and Australia in each other, and that's part of its enduring nature.

"From technology to capability, to intelligence, all of those things being utterly essential to Australia's interest, rather than pursuing self reliance."

Mr Hughes said the Albanese government had been practical in stepping back from the challenging aspects of the Trump administration to understand the "enduring concept" of the alliance.