BILLIONS of dollars of superannuation savings could be unlocked for "nation building" as the Federal Government searches for ways to insulate the economy against the global meltdown.

The Infrastructure Minister, Anthony Albanese, held closed-door talks with super fund chiefs this week in an effort to persuade them to invest some of their trillion-dollar assets in fast-tracked projects that will yield commercial returns.

Mr Albanese confirmed to the Herald that Canberra would be prepared to bankroll more infrastructure if economic conditions worsened and private investors took flight.

The news came as investors lost faith in Australia's largest mining companies.

Rio Tinto's admission it would consider delaying some developments due to weak market conditions prompted a global sell-off in mining shares. Rio's shares fell 16 per cent yesterday, while those of its hostile suitor, BHP Billiton, fell 13 per cent.