WASHINGTON - Vice President Cheney carefully instructed I. Lewis "Scooter" Libby on what to tell journalists to distance Cheney's office from a report that criticized the administration's basis for going to war in Iraq, a White House spokeswoman testified yesterday.

Cathie Martin, former head of public affairs for Cheney's office and now deputy director of communications for President Bush, said the vice president dictated eight talking points to her in July 2003 that were to be passed along to Libby, then Cheney's chief of staff, and others at the White House.

The purpose was to rebut assertions by former U.S. Ambassador Joseph Wilson about a trip he made to Niger, Martin testified at Libby's trial. Wilson had gone to the African country to investigate whether Iraq was seeking to buy nuclear-weapons material there.

Prosecutors contend that Libby lied when he told a federal grand jury he was so focused on national security in 2003 that he confused the facts on the Wilson episode. The grand jury was probing the leak of the identity of Wilson's wife, CIA officer Valerie Plame Wilson.

"Ultimately, it was decided that Scooter would call the two reporters" who were working on stories about whether Cheney's office had asked that Joseph Wilson be sent to Niger, Martin said.

"I recall going in with Scooter and watching him call one of the reporters," she testified. She identified the reporters as Andrea Mitchell of NBC and David Martin of CBS. Martin said she was also present when Libby called Matthew Cooper of Time.

Joseph Wilson has said he found no link between Iraq and Niger during his trip, though the Bush administration suggested that one existed before the United States invaded Iraq in March 2003. In a New York Times op-ed piece July 6, 2003, Wilson accused the administration of distorting intelligence to justify the invasion. Eight days later, columnist Robert Novak disclosed in print that Wilson's wife was a CIA officer.

Libby is accused of lying to investigators probing whether officials deliberately leaked her identity to retaliate against her husband. No one has been charged with the leak itself.

Martin said Cheney dictated talking points during a meeting at his office in the Capitol, seeking to make clear that he had not asked that Joseph Wilson go to Niger, did not know Wilson, and had never seen a report on Wilson's findings.

On cross-examination by Libby attorney Theodore Wells, Martin testified that although she had mentioned to Libby that Wilson's wife worked at the CIA, Martin had not known the wife's name or whether she was undercover. She also said Libby had never mentioned Wilson's wife to her.

Wells, seeking to bolster his argument that Libby and most people have difficulty remembering things, questioned Martin's recollection of key events. He noted that Martin first told the FBI that she found out about the Wilsons in July 2003, then later remembered that that happened in June.

"You forgot an entire month during which you knew?" Wells asked.

"That's correct," Martin responded.

Earlier, U.S. District Judge Reggie Walton told Wells that he would not be allowed to present a defense based on memory in his closing arguments unless Libby testifies.

Libby faces up to 10 years in prison if convicted of obstruction. He is also charged with perjury and making false statements.

Special prosecutor Patrick Fitzgerald indicated he would call former White House spokesman Ari Fleischer as his next government witness.