A leaked draft of the government's 2013 white paper, which will outline the government's defence priorities for the next decade, says Defence will stretch its shrinking budget by ''reforming and rationalising'' its extensive bases and depots.

RAAF Williams Laverton base is thought to be in the crosshairs, as well as the reserves depot in Hawthorn, which is considered prime real estate.

''Australia very clearly faces a new fiscal reality in which we need to balance both fiscal and national security and ensure that Defence resources are focused on the most important priorities,'' the white paper states. ''The government believes that these actions are essential for Australia's defence capability.''

The white paper, the final version of which is set to be released by Defence Minister Stephen Smith by June, also confirms the government's determination to strengthen and lengthen runways in northern Australia and the Cocos Islands for use by drones and other surveillance aircraft.

These are considered essential to scanning waters to the north, and could be used for drones Australia is likely to buy, as well as US unmanned craft.

James Brown, military fellow at the Lowy Institute said there were sensible savings to be made by closing small and inefficient bases, but warned Defence should not ''over-consolidate''.

''The most important thing is that economic rationalism is not the only driver with Defence estate consolidation. Defence needs to be able to stage security forces for natural disasters and events like APEC and CHOGM - just because a base doesn't have an immediate purpose doesn't mean it should be closed.''

There had been ''a lot of pressure'' from property developers on some sites in prime locations.

The debate comes as Prime Minister Julia Gillard prepares to outline in a speech in Canberra on Wednesday the government's new national security strategy for the next five years.

Coalition defence spokesman David Johnston said Defence spending would fall to its lowest level as a share of GDP since 1937.

''Selling bases will provide a Band-Aid solution for the Gillard government to prop up a Defence budget that they have left in an unsustainable mess,'' he said.

''The Defence Minister needs to just come clean, and let the public know which bases are safe and which bases are on the hit-list.''

Australian Defence Association executive Neil James said it was politically difficult to close bases because they were important to local economies, particularly in regional areas.

He blasted any plan to close reservists depots, saying people would quit if they had to travel too far to do their service.

''They're not going to drive 90 minutes … it's not like commuting to work; they're doing this on their own time.''

A spokesman for Mr Smith said the paper was still a draft and would undergo revisions.