Reporter Matt Cooper testified Wednesday he thought I. Lewis "Scooter" Libby had confirmed that a prominent war critic's wife worked at the CIA but acknowledged he never asked the White House aide where he'd heard that.

Cooper, Time magazine's White House reporter at the time, became the second reporter to testify at the CIA leak trial that Libby was a source for their learning that Valerie Plame, wife of ex-ambassador Joseph Wilson, was a CIA operative. Libby claims he only told reporters he had heard that information from other reporters.

The first journalist to testify in the case, 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 Plame from Libby.

Libby, ex-chief of staff to Vice President Dick Cheney, is on trial on charges he lied to the FBI and a grand jury about his conversations with reporters about Plame and obstructed the investigation into how her identity leaked to the public in 2003. He is not charged with the actual leak.

Cooper's appearance allowed defense attorney William Jeffress to ask repeatedly about President Bush's chief political adviser, Karl Rove, because Cooper identified Rove as the first official to tell him about Plame's job at CIA. Cooper said Rove told him that Wilson's wife, rather than Cheney, was responsible for sending Wilson to Niger in 2002.

On July 6, 2003, Wilson claimed in print and on television that what he learned on the trip debunked a report that Iraq was trying to buy uranium there for nuclear weapons. He said Cheney should have learned of his findings long before Bush's used the uranium story in his January 2003 State of Union speech as a justification for war with Iraq.

In his opening statement, defense attorney Theodore Wells claimed the White House was trying in 2003 to blame Libby for the leak in order to protect Rove, although Wells did not explain precisely how that related to the perjury charges against Libby.

Cooper recalled a July 12, 2003, telephone conversation in which he asked Libby whether Wilson's wife worked at CIA and was behind the Niger trip.

Cooper testified Wednesday that Libby responded, "Yeah, I've heard that too," or "Yeah, I've heard something like that, too."

Anticipating the defense attack, Special Prosecutor Patrick Fitzgerald asked whether Libby said where he heard that.

"Not in any way," Cooper replied.

Did he say he heard it from other reporters?

"No," Cooper said.

Cooper also said he didn't take any notes on that exchange and that he had posed his question to Libby "off the record." Later Cooper said off the record information cannot be attributed to the person but can be used to go get the information from others.

Libby attorney Jeffress pounded on Cooper's acknowledgments and also drew the jury's attention to the extensive notes and memos to Time editors that Cooper produced after his talk with Rove.

Jeffress asked Cooper if he ever asked Libby where he'd heard about Wilson's wife.

"I did not," Cooper replied.

His voice dripping with disbelief, Jeffress asked Cooper how he could take his exchange with Libby as confirmation.

"I took it as confirmation," Cooper said.

"Why didn't you put it in your memo to your editors?

"I can't explain that," Cooper replied. "It was late in the day. I didn't write it down, but it is my memory."

"If somebody tells you something off the record, do you take it as confirmation?" Jeffress asked incredulously.

"I did in this case," Cooper replied. "You can use it to go to others and get a more fulsome account" that can be printed.

Miller is a crucial witness in the case. She says she had two conversations about Plame in mid-2003 with Libby, who was Vice President Dick Cheney's chief of staff. Those conversations are at the heart of the trial because they allegedly occurred well before Libby says he learned Plame's identity from another reporter.

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

During a sometimes heated cross-examination Wednesday, defense attorneys pressed Miller to acknowledge that she might have heard about Plame elsewhere.

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

"I don't remember their names. I don't know what you want me to say beyond that," 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."

Jeffress persisted, showing Miller excerpts from her grand jury testimony in which she said her conversation with Libby was "among the first times" she heard about 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?" Jeffress asked.

"I can't be absolutely, absolutely certain, but I have no recollection of an earlier conversation with anyone else," Miller replied.

Special Prosecutor Patrick Fitzgerald's case began as an investigation into who leaked 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.

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