He said Australian politicians and diplomats did not receive ''special access'' to US decision makers and that US-sourced weapons systems were always late, over budget and rarely able to do everything that had been promised.

The New Zealand-born academic, a specialist in global politics and Australian-US relations at the ANU's department of political science and international relations, was asked to speak at the IPAN Canberra Peace Convergence Conference by the Medical Association for the Prevention of War.

He said it was a mistake to assume the US would automatically provide military assistance if Australia was threatened, especially if the aggressor was also important to America.

''America's response to any given threat would be driven by America's own interests at the time,'' he said. ''America only has two 'special' diplomatic relationships … One is with Israel and the other is with France.''

Phyllis Campbell-McRae, the MAPW's Melbourne-based chief executive, said the Canberra conference marked the start of a community debate in Australia over the value of the US Alliance and the need for Australia to frame its own independent foreign policy.

''I think it is just a matter of time before people are actively engaged in reflecting on this [the alliance],'' she said. ''I am not optimistic it will happen overnight but, over time, we can have a national debate … I see this conference as the start.''

Ms Campbell-McRae and Dr McKinley conceded there was strong bipartisan support for the alliance in Coalition and Labor Party ranks.

''It is a bit of a love-in, isn't it,'' Ms Campbell-McRae said. ''[But] in the wake of the Snowden leaks people must realise how closely Australian [agencies] work with the US.''

She said more than 100 people, representing about 50 organisations had taken part in the conference.

Dr McKinley had some serious doubts about whether or not the International Physicians for Prevention of Nuclear War-sponsored movement would achieve a result.

''I think what they [conference participants] want is laudable,'' he said. ''Will they achieve it? I can't see that happening without a major catastrophe.''

Professor Ross Babbage, founder of the Kokoda Foundation, said Dr McKinley was wrong about the alliance. He said it offered Australia security the country could never afford on its own.

''All serious analysis comes to this conclusion,'' he said. ''We get a lot from the relationship in terms of diplomatic assistance, technical expertise and intelligence sharing, but in the end it is more than all of that because of the close personal relationship between the US and Australia.''

Dr McKinley said he had no choice but to give support to the conference despite the low odds of success.

He cited the 1930s Italian writer Antonio Gramsci, who wrote from his fascist prison cell: ''I'm a pessimist because of intelligence, but an optimist because of will.''