Last year, 32-year-old Motassadeq was sentenced to seven years in jail for belonging to a terrorist group. Motassadeq, a Moroccan living in Hamburg, was part of a circle that included Mohamed Atta and two other highjackers that carried out the 2001 suicide attacks in the New York and Washington which killed more than 3,000 people.

In November, Motassadeq was convicted of being an accessory to murder. The court directed a fresh sentencing. The additional charge could double Motassadeq's jail term.

Sentencing going forward despite appeal

Motassadeq has appealed to Germany's Federal Constitutional Court, court officials said Friday.

"The (sentencing) hearing will take place. The constitutional complaint does not suspend that," appellate court spokeswoman Sabine Westphalen told the DPA news agency on Friday.

That hearing is scheduled for Jan. 5.

Motassadeq's defenders, such as attorney Udo Jacob, say the sentence was arbitrary and not well reasoned. Yet the court in Karlsruhe will only review constitutional issues. It could reject the appeal without granting a hearing.

"This is still a thorny path," said Motassadeq's attorney Ladislav Anisic, who submitted the appeal to the constitutional court.

Long legal process

The constitutional court appeal is the latest in a long legal process.

Motassadeq was arrested shortly after the 2001 attacks. In 2003, he was sentenced to 15 years in jail. But that verdict was overturned in 2004 because US authorities had refused to allow the court to question top al Qaeda suspects in US custody.

At his retrial, the court found no evidence that Motassadeq had been directly involved in the attacks. But he was found to have handled the highjackers' bank transfers and to have covered up their whereabouts.

Motassadeq was free on bail until November, when he was re-arrested after his conviction for being an accessory to murder.