Nichols admitted to prosecutors in a signed statement that he helped Timothy McVeigh make the bomb that killed 168 people in the Alfred P. Murrah Federal Building in 1995, The Oklahoman reported. McVeigh was put to death for masterminding the attack.
"McVeigh told me what to do," Nichols said in the statement, which was prepared with the aid of his attorneys.
"Even though he was convicted at both trials, there's always been some lingering doubt among some, and maybe this will help clear up some of the lingering doubt," Oklahoman reporter Nolan Clay told CBS Radio News.
Nichols, 49, is serving life sentences without parole for separate convictions in state and federal courts for his role in the bombings. Juries in 1997's federal trial and the state trial this June deadlocked over whether he should be sentenced to death.
According to the statement, Nichols knew of no other conspirators in the attack and said he did not know which building McVeigh had chosen as a target until reading about it after the bombing.
"He never testified at trial, he's denied it in the past, and his attorneys at trial, both trials, claimed ... that the bomber Timothy McVey had help from others and that Mr. Nichols was set up," said Clay.
Nichols' admission was made as his attorneys tried to persuade state prosecutors not to seek the death penalty. His statements are similar to what McVeigh told biographers before his June 2001 execution.
Negotiations for a plea deal fell through, however, because prosecutors believed Nichols was not forthcoming enough.
District Attorney Wes Lane said although the document underscores Nichols' involvement in the bombing, it also reveals how little Nichols was willing to tell prosecutors, including his refusal to "tell us where certain bomb-making materials are still hidden, even to this day."
Nichols' attorneys declined to comment for Sunday's story.
In the statement, Nichols admitted he helped McVeigh obtain the bomb's ingredients: ammonium nitrate fertilizer from a farmers co-op in Kansas and nitromethane racing fuel from a racetrack in Texas.
He also admitted picking McVeigh up in downtown Oklahoma City on Easter 1995 — three days before the April 19 attack. McVeigh had driven from Kansas to Oklahoma City to park the getaway car, according to evidence at the trials.
Nichols described in detail "going to Oklahoma city to help plant the getaway car and the actual making of the bomb, and he went into detail about how the bomb was made beside a lake in Kansas," Clay said.
"The bomb was constructed at Geary Lake. The only people present were Timothy McVeigh and Terry Nichols," Nichols said in the statement.
Nichols denied knowing anyone else, including McVeigh's friend Michael Fortier, had a role in the bombing.
Fortier is serving a 12-year federal prison sentence for knowing about the bomb plot and not telling authorities, for helping McVeigh move and sell stolen guns and for lying to FBI agents after the bombing.