WASHINGTON (AP) – Former New York Times reporter Judith Miller acknowledged Wednesday that she had conversations with other government officials and could not be “absolutely, absolutely certain” that she first heard about an outed CIA official from I. Lewis “Scooter” Libby.

Mr. Libby’s attorneys seized on the hesitation and tried to portray Ms. Miller as someone who selectively remembers some conversations and not others.

Ms. Miller is a crucial witness against Mr. Libby in his perjury and obstruction trial. She says she had two conversations about CIA operative Valerie Plame in mid-2003 with Mr. Libby, who was Vice President Cheney’s chief of staff. Those conversations are at the heart of the trial because they allegedly occurred well before Mr. Libby says he learned Ms. Plame’s identity from another reporter.

Mr. Libby’s defense strategy revolves around showing jurors that he didn’t lie about his conversations with Ms. Miller and others, but simply forgot them. If defense attorneys can cast doubt on Miller’s memory and her story, it would bolster Mr. Libby’s case.

During a sometimes heated cross-examination Wednesday, defense attorneys pressed Ms. Miller to acknowledge that she might have heard about Ms. Plame elsewhere. In mid-2003, Ms. Miller was investigating allegations by Ms. Plame’s husband, Ambassador Joseph Wilson, that the Bush administration ignored certain prewar intelligence on Iraq.

Attorney William Jeffress asked Ms. Miller to recall the other government officials she spoke to and explain how Mr. Wilson’s name and phone number got into her notebook prior to the conversation with Mr. Libby.

“I don’t remember their names. I don’t know what you want me to say beyond that,” Ms. Miller said, adding moments later, “I know I had several conversations but there is no reference to them in my notebook and I have no independent recollection.”

Mr. Jeffress persisted, showing Ms. Miller excerpts from her grand jury testimony in which she said her conversation with Mr. Libby was “among the first times” she heard about Ms.Plame but couldn’t be certain it was the first.

“You’re not absolutely certain you first heard that Mr. Wilson’s wife worked at the CIA from Mr. Libby?” Mr. Jeffress asked.

“I can’t be absolutely, absolutely certain, but I have no recollection of an earlier conversation with anyone else,” Ms. Miller replied.

Special Prosecutor Patrick Fitzgerald’s case began as an investigation into who leaked Ms. Plame’s name to reporters at a time when her husband was criticizing the administration. Three years later, nobody has been charged with the leak. Mr. Libby is accused of obstructing the case and lying to investigators.

Former Time magazine reporter Matthew Cooper followed Ms. Miller on the stand and testified briefly before the court’s lunch break Wednesday. Mr. Cooper said that during a July 12, 2003 conversation, he asked Mr. Libby whether Mr. Wilson’s wife was involved in sending Mr. Wilson on a fact-finding trip to Niger.

Mr. Cooper said Mr. Libby responded, “Yeah, I’ve heard that too,” or “Yeah, I’ve heard something like that, too.”

Mr. Cooper said he first learned about Ms. Plame from White House aide Karl Rove and said Mr. Libby’s confirmation was off the record. Libby’s attorneys say he was simply repeating what he had learned from another reporter, NBC’s Tim Russert. Mr. Cooper was to continue testifying Wednesday afternoon.

Mr. Libby’s attorneys also said Wednesday that they want to know more about another Mr. Fitzgerald case involving Ms. Miller. Mr. Fitzgerald has sought to get Ms. Miller’s phone records in an investigation into who leaked the details about an investigation into an Islamic charity.

Theodore Wells, another of Mr. Libby’s attorneys, said he wants to know more about conversations between Ms. Miller and Mr. Fitzgerald in that case. If Ms. Miller feared prosecution in that case, Mr. Wells said, it could motivate her to cooperate in Mr. Libby’s case and thus cast doubt on her testimony.

Journalism organizations have decried this trial, which could see 10 reporters become witnesses. Mr. Jeffress has said that up to seven reporters are on his witness list.