The family of Charles Zentai, the Perth man charged with war crimes, has accepted he will have to be taken into custody tomorrow.

The 88-year-old has been fighting the Hungarian government's attempts to extradite him over the alleged killing of a Jewish teenager in 1944.

The Federal Home Affairs Minister Brendan O'Connor will have the final say on whether he is extradited.

But Mr Zentai's son Ernie Steiner says the Federal Attorney-General's office will not pass on the case to the Home Affairs Minister until his father is in custody.

He says his father's health will suffer.

"My father is an innocent man, so the prospect of him going to prison is a very humiliating thing and also it's really adverse to his health," he said.

abc.net.au