An accomplice in the 1995 Oklahoma City bombing has been sentenced to life in prison without parole.
Nichols was tried in federal and state courts for his role in the bombing
Terry Nichols was given a life term for each of 161 murder charges relating to the bombing of a federal building, which killed 168 people.
He is already serving a life sentence on federal charges of conspiracy and the involuntary manslaughter of eight federal officers who died in the blast.
His accomplice Timothy McVeigh, who planted the bomb, was executed in 2001.
Plea for forgiveness
Addressing the court for the first time, Nichols read out a statement expressing remorse.
"My heart truly goes out to all the victims and survivors
and to everyone who was affected by the Oklahoma City
bombing," he said, the AP news agency reported.
"Words cannot adequately express the sorrow I have felt over the years for the grief they have all suffered."
He also asked for forgiveness and urged "everyone to acknowledge God".
Passing the sentence, Judge Steven Taylor called Nichols a "terrorist", adding: "I hope that you never have a waking moment that you do
not consider those 161 souls that you took away."
Although Nichols, 49, was at home when the bomb exploded, prosecutors believe he closely helped McVeigh plan the attack and his subsequent escape in a getaway car.
Nichols was found guilty in May of the murder of 160 people who died in the bombing, plus a foetus being carried by one of the victims.
He was spared the death penalty in both trials as neither jury could reach the unanimous decision that he should be executed.
The bombing of the Alfred P Murrah building on 19 April 1995 was the worst act of domestic terrorism in US history.
The blast came from a home-made bomb containing 2,200kg of ammonium nitrate fertiliser and fuel oil packed into a hired van.
It ripped the front off the nine-storey building.
Nineteen of the victims were children, most of whom were in a nursery on the second floor.
The motive for the attack was apparently retaliation against the government for the bloody end to a siege near Waco, Texas, two years earlier to the day, in which 82 members of the Branch Davidian sect died.