President Bush's top political adviser, Karl Rove (search), testified Friday before a federal grand jury trying to determine who leaked the name of an undercover CIA officer.

Rove spent more than two hours testifying before the panel, according to an administration official who spoke only on condition of anonymity because such proceedings are secret.

Rove has been interviewed at least once previously by investigators in the leak case, as have Bush, Vice President Dick Cheney, Secretary of State Colin Powell and other senior administration officials.

White House spokesman Trent Duffy referred questions to the Justice Department.

The special prosecutor in the case, U.S. Attorney Patrick Fitzgerald of Chicago, declined comment through a spokesman.

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 (search) on July 14, 2003.

Novak's column appeared after Plame's husband, former Ambassador Joseph Wilson, wrote a newspaper opinion article criticizing Bush's claim that Iraq had sought uranium in Niger — a claim the CIA had asked Wilson to check out. Wilson has said he believes his wife's name was leaked as retribution.

In a widely quoted remark, Wilson said after a speech in 2003 that it might be "fun to see Karl Rove frog-marched out of the White House in handcuffs." Wilson has accused Rove of spreading word of the Novak column to reporters.