The federal budget may redirect millions of dollars in aid from Papua New Guinea after its decision to close the Manus Island immigration detention centre.
The Australian government pledged a one-off $420 million aid sweetener to PNG in 2013 when the then-Rudd Labor government signed a refugee resettlement deal.
It's understood several hundred million dollars is yet to be spent.
Millions of dollars allocated for a failed refugee resettlement deal with Cambodia might also be redeployed in the federal budget.
Only five refugees accepted the resettlement offer and of those, three have returned to their countries of origin.
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Australia offered Phnom Penh a $40 million aid sweetener for landmine eradication projects, rice milling and electoral reform initiatives.
A further $15 million was allocated to cover resettlement costs.
Immigration Minister Peter Dutton blames the low take-up rates on refugee advocates who have been encouraging refugees on Nauru to stay put.
Mr Dutton refuses to say exactly how much has been spent, indicating it's in the low millions.
The government was in talks with the Philippines last year about resettling refugees from Manus Island in Papua New Guinea.
The fate of the Christmas Island detention centre could also be revealed in the budget.
It had almost 183 detainees as of late March and costs about $243,000 a day to run, close to $1500 per detainee.
There may also be cost blowouts associated with processing the 25,000 asylum-seeker legacy caseload from previous Labor governments.
The government has passed laws to fast-track the claims but there are still lengthy delays.
