WASHINGTON - Former Time magazine reporter Matt Cooper testified yesterday that he thought I. Lewis "Scooter" Libby had confirmed in 2003 that a prominent war critic's wife worked at the CIA but acknowledged never asking Libby where he had heard that.

Cooper became the second reporter to testify at the CIA leak trial that Libby was a source for their learning that Valerie Plame Wilson was a CIA officer. Libby contends he told reporters only that he had heard that information from other reporters.

Libby, former chief of staff to Vice President Cheney, is accused of lying to the FBI and a grand jury about his conversations with reporters about Wilson and of obstructing the investigation into how her identity leaked to the public in 2003. He is not charged with the leak.

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

On July 6, 2003, Joseph Wilson asserted in print and on television that what he had learned in Niger 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 used the uranium story in his January 2003 State of Union speech as a justification for war with Iraq.

Defense attorney Theodore Wells, in his opening statement at Libby's trial, alleged that the White House was trying in 2003 to blame Libby for the leak to protect Rove.

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

Cooper, who was then Time's White House reporter, testified yesterday 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 had heard that.

"Not in any way," Cooper replied.

Did he say he had heard it from other reporters?

"No," Cooper said.

Cooper said he had not taken notes on that exchange and had posed his question to Libby "off the record." Later, Cooper said that off-the-record information cannot be attributed to the person but can be used to go get the information from others.

Earlier yesterday, the first journalist to contradict Libby's version, former New York Times reporter Judith Miller, acknowledged she could not be "absolutely, absolutely certain" that she first heard about Valerie Wilson from Libby.

But she added that "I have no memory of a prior discussion with anyone else" and that her notes do not reflect any prior discussion.

Miller testified she had two conversations with Libby about Valerie Wilson well before Libby says he learned from another reporter that Joseph Wilson's wife worked at the CIA.

Jeffress advised the judge that the defense wants to call New York Times managing editor Jill Abramson to rebut Miller. Abramson was Miller's bureau chief in Washington in 2003. Jeffress said he anticipated that the Times would try to quash a subpoena for her appearance and that the defense might need time to fight that battle in court.