''Australia has an abiding interest in a safe, secure and reliable United States nuclear stockpile,'' Defence Department officials wrote in confidential 2009 submission to a US review of nuclear readiness. ''Australia would only expect the US to come to our aid in circumstances where we were under threat from a major power whose military capabilities were simply beyond our capacity to resist. But there remains one area of Australian security for which we remain entirely dependent on the US - that of extended nuclear deterrence.''

The submission is one of a bundle of secret defence documents obtained by the International Campaign to Abolish Nuclear Weapons under freedom of information law.

Defence officials acknowledged the human cost of a nuclear war would be ''staggering'' but said without a time frame for eradicating atomic weapons - and with ''complex and prolonged'' negotiations likely in the meantime - the nuclear option should remain.

A British report last month estimated the US would spend $US700 billion ($A680 billion) on the nuclear weapons industry over the next decade.

Mr Rudd had set up an international panel of experts in 2008, chaired by former foreign minister Gareth Evans, to help chart a path to nuclear abolition. In a 2009 note, classified secret to the then defence minister, officials said while the Evans commission would be important for Australia's treaty obligations to contribute to nuclear disarmament, ''our desire to support its goals must be balanced against our strategic interest in ensuring stability through ensuring a credible US extended deterrence''.