DENVER (AP) _ Terry Nichols says he should only serve four to six years in prison for his role in the Oklahoma City bombing that killed 168 people.

Nichols also asked for a new trial Monday, contending the government failed to disclose ``tens of thousands'' of witness statements in the April 19, 1995, bombing of the Alfred P. Murrah Federal Building.

Prosecutors pressed for a sentence of life in prison without parole, but Nichols' attorneys said he deserves the lesser sentence because he faces a state trial in Oklahoma on charges that he was acquitted of at his federal trial.

Nichols was convicted by a federal jury in Denver of conspiracy and involuntary manslaughter but acquitted of murder. His sentencing date has not been set.

Prosecutors in Oklahoma have vowed to try him for murder and seek the death penalty at the state trial. Co-conspirator Timothy McVeigh, sentenced to death in a federal trial, also faces state charges.

In its bid for a new trial, Nichols' attorneys said they learned only late in the case that the government failed to disclose ``an enormous number'' of witness statements considered leads by the FBI.

Among them were notes from FBI agent Chris Budke that showed a witness told him it was a gray pickup truck, not a dark pickup like the one owned by Nichols, that was seen at a park where investigators said the bomb was built.

Also Monday, Nichols' wife filed a motion in federal court requesting the return of $3,880 in gold, silver and cash.

Marife Torres Nichols claims the FBI has refused repeated requests to return nine gold coins, three silver coins and $170 in cash seized from Nichols' Herington, Kan., home four days after the bombing.

She said the government returned $4,830 in cash in May 1995, but there was no accounting for the remaining $170.