(CNN) -- A Nigerian man accused of attempting to detonate an explosive device in his underwear aboard a flight to Detroit last Christmas pleaded not guilty Thursday to new charges, authorities said.
Umar Farouk AbdulMutallab was indicted on two new counts -- conspiracy to commit an act of terrorism transcending national boundaries and possession of a firearm or destructive device in furtherance of an act of violence. He faces a maximum sentence of life in prison on the new charges and on six counts brought against him in early January if he's convicted.
During a 20-minute hearing Thursday, AbdulMutallab stood mute when asked his plea, so U.S. District Judge Nancy Edmunds entered a not guilty plea on his behalf, said Rod Hansen, court spokesman.
"The government asked for a trial date, but the judge said that because the superseding indictment had just been filed the day before, she wanted to give the defendant and his standby attorney time to look it over," Hansen said. A pretrial conference was set for January 12.
The initial charges against AbdulMutallab included attempted use of a weapon of mass destruction and willful attempt to destroy and wreck an aircraft within the jurisdiction of the United States. However, the first batch of charges did not include the specific word "terrorism." AbdulMutallab entered a not guilty plea in January.
In September, AbdulMutallab told Edmunds he did not want to be represented by the public defenders assigned to his case and would like to act as his own lawyer. Edmunds agreed but appointed a standby counsel for him in case he needs help.
Asked on Thursday by Edmunds if he still wants to represent himself, a calm AbdulMutallab answered, "Yes, ma'am," according to Hansen. The defendant was wearing a khaki-colored prison jumpsuit. He was handcuffed and shackled as he was led into court, but the cuffs and chains were removed before the judge entered.
Also in September, AbdulMutallab asked Edmunds how to proceed if he would like to plead guilty to some charges.
The judge told him that was something his standby lawyer could assist him with.
AbdulMutallab was a passenger on Northwest Airlines Flight 253 en route from the Netherlands to Detroit on Christmas Day.
According to the indictment, he went to the bathroom shortly before the plane was to land. When he returned to his seat he said his stomach was upset and he pulled a blanket over himself. Prosecutors allege he then tried to ignite an explosive device made of PETN and TATP that was hidden in his underwear.
Passengers and flight crew members subdued him. U.S. officials say the terror group al Qaeda in the Arabian Peninsula was behind the alleged bombing attempt.
CNN's Susan Candiotti and Deb Feyerick contributed to this report.