Germany's highest court says it has received an appeal from John Demjanjuk's lawyer seeking to block the 89-year-old's trial.
However, the Federal Constitutional Court did not say Monday when it might rule on the request to halt the trial, which is scheduled to open in Munich on Nov. 30.
Prosecutors have charged the retired auto worker with being an accessory to the murder of thousands at the Sobibor death camp in Nazi-occupied Poland.
Lawyer Ulrich Busch said last week he would seek to halt the trial. He has cited health concerns among other issues.
The Ukrainian-born Demjanjuk was deported from the United States in May. He maintains that he was a Red Army soldier who was held as a prisoner of war and never hurt anyone.