A former White House aide facing perjury charges will get only a prosecutor's summary of classified documents assessing the damage to national security from the leak of a CIA officer's identity, a federal judge ruled Friday.

U.S. District Judge Reggie B. Walton also said lawyers for I. Lewis "Scooter" Libby must settle for a prosecutor's version of information contained in secret government documents that describe CIA officer Valerie Plame's employment history.

Libby, former chief of staff to Vice President Dick Cheney, is charged with perjury and obstruction of justice for lying to the FBI and a federal grand jury about how he learned about Plame's CIA status and what he subsequently told reporters about her. His trial is scheduled for January.

Walton said Special Counsel Patrick Fitzgerald convinced him that providing Libby's lawyers with classified documents describing the consequences, if any, of Plame's outing and her CIA employment history "could cause serious if not grave damage to the national security of the United States."

In a separate order Friday, Walton reiterated his denial during a hearing last month of Libby's requests for any documents generated by officials in the White House, CIA and State Department about a trip Plame's husband, former U.S. Ambassador Joseph Wilson, took at the CIA's request in early 2002 to Niger.

The CIA sought to determine whether there was any truth to reports that Saddam Hussein's government had tried to buy yellowcake uranium from Niger to make a nuclear weapon. Wilson discounted the reports. Nevertheless, the allegation wound up in President Bush's 2003 State of the Union address.

Syndicated columnist Robert Novak named Plame in a column on July 14, 2003, eight days after Wilson alleged in an opinion piece in The New York Times that the Bush administration had twisted prewar intelligence on Iraq to justify going to war.

During a May 5 court hearing, Theodore Wells, Libby's lawyer, told Walton that he needs government records of Wilson's trip, Plame's role in the CIA decision to send him to Africa and reports done after his return to show that Libby was not part of a plot to use Plame to smear the former ambassador for criticizing the administration.

In an eight-page order Friday, Walton said Libby is entitled to those documents if they show he was involved in an effort to counter Wilson's charges on the merits.

But Walton repeated his desire to prevent Libby's defense team from turning the trial into a debate on the legitimacy of the war in Iraq or the accuracy of Wilson's statements in the op-ed piece in The Times.

The judge said what matters is whether Libby lied to a grand jury and the FBI about what he told three reporters — Judith Miller of The Times; Matthew Cooper of Time magazine; and Tim Russert of NBC — about Plame.

"The prosecution of this action, therefore, involves a discrete cast of characters and events," Walton wrote.

Fitzgerald has revealed in court filings that Cheney was particularly upset by Wilson's article and played a key role in a White House effort to counter the former ambassador's accusations.

In doing so, Cheney was a pivotal player in declassifying portions of a highly secret intelligence assessment so Libby could share information on Iraq with a select group of reporters, according to Fitzgerald's court filings.

Walton accepted Fitzgerald's promise that he does not plan to insinuate to a jury that Libby — or Cheney — did anything improper by releasing some information from the 2002 National Intelligence Estimate.

Because it won't be an issue, the judge said, Fitzgerald doesn't have to give Libby any documents the prosecutor has gathered that relate to the White House's decision to make public portions of the intelligence assessment.