Lawyers for Oklahoma City bombing conspirator Terry Nichols have filed an appeal with the U.S. Supreme Court, based partly on thousands of pages of FBI documents withheld from defense teams for Nichols and Timothy McVeigh.

John Richilano said the request for a rehearing was filed shortly before midnight Friday.

Richilano was reviewing the FBI documents, delivered Thursday, after the Justice Department disclosed that the papers had been mistakenly withheld.

The FBI miscue prompted U.S. Attorney General John Ashcroft to postpone the May 16 execution of McVeigh until June 11.

"I was stunned and dismayed. I couldn't believe after all these years the U.S. government withheld several thousand pages of documents in the most important case of the century," Richilano said Saturday.

Nichols and McVeigh were both convicted in Denver for their roles in the April 19, 1995, bombing of the Alfred P. Murrah Federal Building that killed 168 people in Oklahoma City. Nichols is serving a life sentence.

Last month, Richilano filed notice of plans to appeal the 10th U.S. Circuit Court of Appeals' decision to refuse Nichols a new trial.

The court in December denied an appeal for a new trial based on assertions by Nichols' lawyers that the prosecution had failed to disclose evidence that could have helped their client. Midnight Friday was the deadline for seeking a review of that dismissal.

It apparently was coincidental that the government's admission it had failed to disclose evidence came on the last day for Nichols' attorneys to ask the Supreme Court to review its earlier denial.

Richilano said he has not yet talked with Nichols.

Richilano told The Associated Press that "a substantial number of the documents" dealt with a John Doe No. 2 and FBI interviews concerning John Doe No. 2 from offices around the country.

Richilano has asked Nichols's former trial attorney, Michael Tigar, to discuss the case with him. Tigar told CNN that an appeal will be filed.

"He is assisting his former client in any way he can," Richilano said. "He was the one who tried the case, and he's most familiar with all the withheld materials."