Lawyers for a former White House official convicted of obstruction of justice and perjury, I. Lewis Libby Jr., are asking that he be sentenced to probation and spared a prison term.

“It is not necessary to incarcerate Mr. Libby to promote respect for the law or to serve the interests of general deterrence,” the defense team wrote in court papers filed yesterday.

Libby is scheduled to be sentenced Tuesday by Judge Reggie Walton, who oversaw the trial that led to Libby ‘s convictions in March.

In its plea for leniency, the defense detailed Libby’s history of community and government service, which includes service to the State Department and Defense Department before he became Vice President Cheney’s chief of staff in 2001.

“Mr. Libby did not seek high office for partisan purposes or for personal aggrandizement, and he was most comfortable toiling behind the scenes, out of the public eye,” the defense team, led by Theodore Wells Jr. and William Jeffress Jr., wrote.

The prosecution has urged Judge Walton to send Libby to prison for between 30 and 37 months.

The defense’s new filings did not address the key issue of whether Libby should get bail pending appeal if he is sentenced to jail. Many of Libby’s supporters have called on President Bush to issue a pardon. He would be pressed to do so immediately if Libby is ordered to report to jail forthwith.

The case against Libby was brought by a special prosecutor, Patrick Fitzgerald, in connection with an investigation into the disclosure of the identity of a CIA operative, Valerie Plame. No one was ever charged for leaking, but Libby was accused of lying when he told investigators and a grand jury that he thought for a time that journalists were the first to inform him of Ms. Plame’s CIA connection.

A jury convicted Libby on four felony counts: obstruction of justice, lying to the FBI, and two counts of perjury. He was acquitted on one count of perjury.

“This is the rare case where the statements by the defendant that were found to be false did not cover up any underlying crime,” the defense wrote, while quickly adding, “We do not mean to suggest that the absence of an underlying offense excuses obstruction and perjury.”

In their sentencing filing last week, prosecutors argued for the first time that Ms. Plame was a covert CIA operative covered by a federal law protecting the identities of such agents. In its response yesterday, the defense took umbrage at the prosecution for belatedly making inflammatory claims about Ms. Plame, whose role at the CIA was put off limits at Libby’s trial.

“The government has now adopted a new position on Ms. Wilson’s status in a brazen attempt to convince the Court that Mr. Libby should be punished as if he outed a covert CIA official or mishandled classified information — a position it carefully avoided taking before or at trial,” defense lawyers wrote, referring to Ms. Plame by her married name. They complained that the prosecution was making factual assertions that Libby was denied permission to explore before his trial.

“This is tantamount to asking the Court and Mr. Libby to take the government’s word on Ms. Wilson’s status, based on secret evidence, without affording Mr. Libby an opportunity to rebut it. Such a request offends traditional notions of fairness and due process,” the defense wrote.

The defense team also took issue with the prosecution’s claim that Ms. Plame’s temporary assignments overseas rendered her a covert agent. The law defines a covert agent as a classified CIA employee who has “served outside the United States” in the past five years.

“It is not clear that engaging in temporary duty travel overseas would make a CIA employee who is based in Washington eligible for protection under the IIPA. In fact, it seems more likely that the CIA employee would have to have been stationed outside the United States to trigger the protection of the statute,” the defense wrote.

Libby faces a maximum possible sentence of 25 years in prison, though he is likely to be sentenced to far less under federal sentencing guidelines. Judges are not required to follow the guidelines, but they usually do.