The Munich State Court ruled 10 days ago that Demjanjuk, 89, was fit to stand trial but limited the time he can be tried each day to two sessions of 90 minutes each, CNN reported.
Demjanjuk, a native Ukrainian, has long denied any role in the Holocaust and claimed he was a prisoner of war, not a death camp guard.
Demjanjuk was deported in May from the United States to Germany, where he was wanted for alleged involvement in the killings as an SS guard at Sobibor, a World War II Nazi death camp in Poland.
The trial in Germany would be Demjanjuk's second war crimes trial. He was convicted in an Israeli trial in the 1970s and sentenced to death, but the sentence was overturned when mistaken identity was proven.