A former White House aide, I. Lewis Libby, may have disclosed conclusions from a highly classified government report on Iraq to journalists before the report was declassified by President Bush, federal prosecutors said in a new court filing.

Mr. Libby resigned as chief of staff to Vice President Cheney when he was indicted last year on obstruction of justice and perjury charges in connection with an investigation into the leak of the identity of a CIA official, Valerie Plame.

The special prosecutor who oversaw the probe, Patrick Fitzgerald, has not charged Mr. Libby or anyone else for participating in the leak. It emerged recently that the first public account of Ms. Plame’s employment, in a 2003 column by Robert Novak, was triggered by comments from a State Department official, Richard Armitage.

Attorneys for Mr. Libby have asked that the prosecution be precluded from arguing at trial that Mr. Libby acted improperly or illegally when he discussed a National Intelligence Estimate on Iraq with the press. The issue ties into the criminal case because in some of the conversations about the estimate, Mr. Libby is alleged to have mentioned Ms. Plame or answered a question about her.

In April, The New York Sun first reported that Mr. Libby said he disclosed the intelligence report on Iraq at the direction of Mr. Cheney, who said he had obtained the permission of Mr. Bush to release the findings of the closely held document.

In court papers filed Wednesday, Mr. Fitzgerald reaffirmed that he does not plan to argue that Mr. Libby was wrong to disclose the report’s conclusions to journalists. However, the prosecutor said he wants the ability to attack Mr. Libby’s credibility if he or his lawyers argue that all his disclosures from the Iraq report were clearly authorized by his superiors.

“The timing of the declassification relative to defendant’s disclosure of the NIE to reporters is unclear,” Mr. Fitzgerald wrote, urging Judge Reggie Walton to reject the defense proposal. “The government should not be muzzled from raising any questions about the declassification’s timing.”

According to the prosecutor, Mr. Libby testified initially that he was told of the declassification just prior to a July 8, 2003, meeting he had with Judith Miller of the New York Times. However, Mr. Fitzgerald said Mr. Libby “was unsure” whether the declassification took place prior to meetings he had with a Washington Post reporter, Bob Woodward, on June 27 of that year, and with another Times journalist, David Sanger, on July 2.

“Defendant testified that he recalled a ‘go-stop-go’ sequence in discussions concerning authorization to disclose the NIE, that is, he was authorized to disclose, then he was instructed to hold off, and then later told again to disclose,” Mr. Fitzgerald wrote. He also said Mr. Libby testified that he may have “slipped” in discussing with Mr. Sanger the report’s conclusion that Iraq was “vigorously trying to procure” uranium.

“The government simply wishes to make clear that it cannot affirmatively agree that each time defendant disclosed the NIE, he was authorized to do so,” Mr. Fitzgerald said.

In a separate filing, the prosecutor also asked Judge Walton to reject a defense motion seeking to bar any discussion at Mr. Libby’s trial about the extensive legal wrangling surrounding efforts to force reporters to testify before the grand jury investigating the leak. One journalist, Ms. Miller, spent 85 days in jail after refusing to testify about her conversations with Mr. Libby.

Mr. Fitzgerald said the defense was seeking “free rein” to argue Mr. Libby had no reason to lie because he thought reporters would testify, when, in fact, he knew that the journalists were likely to go to some lengths to avoid testifying. The prosecutor also disputed the defense claim that Mr. Libby unequivocally exhorted Ms. Miller and other reporters to testify.

Mr. Libby’s lawyers have said his defense will argue that he misremembered certain conversations amid the intense press of national security concerns and terrorist threats he dealt with daily. On Monday, Judge Walton ruled that the government was being too stingy in crafting descriptions that jurors could be shown of the classified security matters Mr. Libby handled. However, the judge withdrew that ruling yesterday, citing a problem with its legal rationale.

Mr. Libby’s trial is set to begin in January.