The Government is yet to determine where it will source $2 billion of its $4.7 billion equity commitment to the National Broadband Network (NBN).
Appearing before Senate Estimates, the Department of Finance and Deregulation faced a series of questions over the Government's current and planned equity injections into NBN Co.
NBN Co had received $260 million to date and would receive another $52 million "sometime this month or late next month", bringing its total funding to $312 million by the end of June.
A further $2.06 billion had been allocated from the Building Australia Fund (BAF) next year, along with $300 million that was "projected to be raised from Aussie infrastructure bonds", Department secretary David Tune said.
Sources for the remaining $2 billion were "not yet determined", Tune said.
He said it was "possible" that the extra money could be drawn down from the BAF.
More money could also come from issuing further infrastructure bonds, although the Department was also unable to provide guidance on the total amount that might be drawn from Aussie infrastructure bonds over the course of the Government's investment in the NBN.
"All that's settled at the moment is the 2010/11 issuance [for $300 million]," Tune said.