Attorneys for I. Lewis "Scooter" Libby formally asked a federal judge Thursday to delay the former White House aide's 2 1/2-year prison sentence, a request the judge has indicated he's not inclined to grant.

In documents filed with the court, Libby's attorneys say they have a good chance of winning an appeal of Libby's conviction for perjury and obstruction in the CIA leak case. Jurors found that Libby lied to investigators about how he learned that the wife of an outspoken war critic worked for the CIA, and whom he told.

During Libby's monthlong trial, attorneys disagreed with several of U.S. District Judge Reggie B. Walton's decisions, including prohibiting them from presenting an expert witness to testify that Libby could have simply forgotten his conversations because of the stress of his daily job.

Defense attorneys argued in their filing Thursday that Special Prosecutor Patrick Fitzgerald lacked the constitutional authority to bring charges against Libby, the former chief of staff to Vice President Dick Cheney. They also said they were unfairly prohibited from questioning NBC reporter Andrea Mitchell about why she said lots of journalists knew Plame's identity.

At Libby's sentencing hearing Tuesday, Walton said he sees no reason to allow Libby to remain free pending appeal. If he rules that way, Libby's attorneys have said they will ask an appeals court to put the prison term on hold.

A delay would give President Bush more time to consider pardon requests from Libby's supporters, who say the loyal aide was caught up in a political investigation and does not deserve prison time.