The UN Committee against Torture is this week expected to address the powers of Australia's child abuse royal commission, with implications for Australian-Vatican relations.

The committee will discuss its review into Australia's adherence to the convention against torture in Geneva on Friday.

Abuse survivors campaigner Nicky Davis says she hopes the UN delivers a firm ultimatum.

"I hope the UN CAT very clearly puts the Australian government on notice that anything less than serious, widespread reform to ensure that in future these crimes are properly investigated, offenders are held responsible, re-offending is prevented, and survivors helped to recover, will be totally unacceptable," she said.

Ms Davis, the head of Survivors Network for People Abused by Priests (SNAP) says the issue being addressed by the UN is "a political and legal system, that values the impunity of powerful predators far above the recovery of survivors or the safety of children".

During the UN's two-day review in November, an Australian government delegation was asked about Canberra's response to Cardinal George Pell's evidence to the sex abuse royal commission that a request for documents held by the Vatican on priests who abused children in Australia was "unreasonable".

Cardinal Pell told the commission that Vatican documents would be, and had been, supplied but it was not appropriate to hand over all relevant documents as they were private and internal to a sovereign state - the Vatican City.

In reply to questions about the government's response, the delegation said the royal commission "had statutory powers to compel the provision of documents should it wish to do so".

It also said it was up to the commission to pursue the Vatican.

The vice-chair of the UN committee Felice Gaer, asked the delegation for a specific answer on whether the Australian government agreed that such documentation was the private property of the Vatican and whether the request was unreasonable.

A spokesman for the attorney-general told AAP the department had nothing further to add to the public reply given at the UN hearing.

He would not say whether Australia had answered Ms Gaer's questions but said "it is a matter for the royal commissioner (Justice Peter McClellan) to determine how to proceed with its inquiry."

The UN committee had received submissions from two non-government organisations representing survivors of childhood sexual abuse.

The committee will hold a press conference on Friday in Geneva which will also cover Australia's immigration detention and offshore processing of asylum seekers.

The royal commission said on Wednesday it was taking further steps to obtain documents from the Vatican relating to the sexual abuse of children in Australia.