THE Rudd Government has acknowledged that the supremacy of the US has begun to fade and Australia is preparing for an uncertain future in which it can no longer rely on the protection of its main ally.

In a fundamental shift in defence plans, the Government has explicitly declared that US primacy in the Asia-Pacific - the bedrock of the nation's security since World War II - may be ending. The change, caused by the rise of new great powers such as China, is set to produce growing regional tensions and a "sudden deterioration" in Australia's security.

A 20-year defence blueprint, to be released by the Prime Minister, Kevin Rudd, today, prepares for a multibillion-dollar build-up of naval and air forces to ensure that Australia can defend its northern and sea approaches.

It says a regional shake-up is under way but US supremacy will not be blunted before 2030 and assesses the chances of an attack on Australia in the short term as "very remote".

The white paper, Defending Australia In The Asia Pacific Century: Force 2030, is the first since 2000 and outlines a range of security threats, including instability caused by the financial crisis, cyber warfare, failed states in the Pacific, Islamist terrorism, weapons of mass destruction, and climate change.