The United Nations refugee agency has told the Australian government it will not play any part in processing asylum seekers sent to Nauru or Manus Island.
The federal government expects to be able to house 500 asylum seekers in Nauru by the end of September.
PNG has formally given the approval for a processing centre on Manus Island.
UNHCR regional representative Richard Towle told The World Today on the ABC that the agency will monitor the policy, but will not help the Australian government with the plan.
"Australia may choose to transfer physically people to other jurisdictions, but we believe that under international law, very clearly Australia is not absolved of its legal responsibilities to protect people through all aspects of the processing and solutions," he said
Mr Towle said concerns remain surrounding the indefinite detention and mental health of asylum seekers.
"It's difficult to maintain an adequate level of health and care for people who may already be suffering from trauma as a result of their persecution and leaving their countries of origin and the voyages towards Australia," he said.