Federal authorities and the family of Charles Zentai are tight-lipped on the process that could see the accused Nazi war criminal taken into custody.

Zentai, 88, lost a court appeal earlier this month to avoid extradition to Hungary on a war crimes charge of killing a Jewish teenager in Budapest in 1944.

The full bench of the Federal Court granted a stay of 14 days on the execution of the extradition warrant on October 8.

The stay lapses at 4.30pm (WST) on Thursday, when Zentai is to be automatically remanded in custody as part of the legal process, subject to his surrender or any further legal steps undertaken by his lawyers.

Neither the Australian Federal Police, the Attorney-General's Department nor the Director of Public Prosecutions would comment on arrangements for Zentai's possible detention.

Zentai's son Ernie Steiner, who has acted as his father's spokesman since a warrant was issued for his arrest in 2005, declined to answer calls.

He issued an SMS message to media saying he had been advised not to pass on details of Thursday's arrangements because of his father's heart condition.

'I am sorry but owing to extreme media pressure aggravating my father's heart condition yesterday I am advised not to pass on arrangements for today,' Mr Steiner told AAP.

Doctors have affirmed Zentai's poor medical condition, which has helped keep him out of custody since Perth magistrate Barbara Lane last year ruled he was eligible to be surrendered for extradition to face the war crimes charge.

A spokeswoman for the Attorney-General's Department said the legality of Zentai's detention, in accordance with Australian extradition arrangements, was upheld by the High Court in 2006.

The court dismissed an application by Serbian Dragan Vasiljkovic to have the Extradition Act ruled invalid.

The spokeswoman said any further legal action was a matter for Zentai and his lawyers.

'Subject to any further stay, when the 14-day stay ends, he'll be committed to prison,' the spokeswoman said.

Zentai's lawyers this week had been pursuing ways to prevent him being taken into custody.

This included approaches to the attorney-general, who has the final say in his possible extradition.

Mr Steiner said on Tuesday he had been advised the attorney-general could not act until his father was in custody.

Another alternative avenue for his father to avoid custody was to seek a writ of mandamus in the High Court, he said.

If issued, a writ of mandamus could compel the Attorney-General's Department to deal with the case.

bigpondnews.com