A federal judge has refused to quash a subpoena that requires a Time magazine reporter to testify before a grand jury investigating the leak of an undercover CIA (search) officer's identity.

Lawyers for reporter Matthew Cooper argued that he already had testified in a deposition in the case on Aug. 23, when he discussed a conversation he had had with Lewis "Scooter" Libby, Vice President Dick Cheney's (search) chief of staff. Special prosecutor Patrick Fitzgerald said he needed additional information due to an "unanticipated shift" in the grand jury's investigation.

U.S. District Judge Thomas Hogan said the prosecutor's latest request is not "unreasonable or oppressive" conduct.

"The fact that special counsel did not exhaust all relevant subject matter during Mr. Cooper's first deposition shows that Mr. Fitzgerald was proceeding in the investigation with great deference to Cooper's status as a member of the press," Hogan said in an order made public on Wednesday.

The investigation concerns whether a crime was committed when someone leaked the identity of CIA officer Valerie Plame (search), whose name was published by syndicated columnist Robert Novak on July 14, 2003. At least five reporters have been subpoenaed to testify in the case.