Columnist Bob Novak, who first published the identity of covert CIA officer Valerie Plame, says he is confident that President Bush knows who leaked Plame's name.

Novak said that "I'd be amazed" if the president didn't know the source's identity and that the public should "bug the president as to whether he should reveal who the source is."

Novak's remarks, reported in the Raleigh, N.C., News & Observer, came during a question and answer session Tuesday after a speech sponsored by the John Locke Foundation, a conservative think tank.

Democratic Sen. Charles Schumer urged Bush to identify Novak's source or to say that he does not know who it is.

In 2003, Novak exposed Plame's identity eight days after her husband, former U.S. Ambassador Joseph Wilson, accused the Bush administration of manipulating prewar intelligence to exaggerate the Iraqi threat. In the column disclosing Plame's CIA status, Novak said the sources for his column were two administration officials.

The identity of Novak's sources has been one of the secrets in the CIA leak investigation.

Bush's top political adviser, Karl Rove, is one of Novak's sources, according to people close to the investigation, but his other source is not publicly known.

Novak apparently is cooperating with the criminal investigation of Special Counsel Patrick Fitzgerald, though the journalist has never said so.

The prosecutor has aggressively pursued contempt of court orders against reporters who have refused to cooperate and Novak is not among those who have become embroiled in court battles in the probe.

Schumer, D-N.Y., urged Bush to share the identity of Novak's sources if the president knows.

"You are in a position to clear this matter up quickly," Schumer said in a letter to the president on Wednesday.

"Unlike Mr. Novak, who can claim an interest in maintaining the confidentiality of his sources, there is no similar privilege arguably preventing you from sharing this information," Schumer wrote.

"You have repeatedly suggested that you would like to get to the bottom of this affair," Schumer reminded Bush. "At one point, in 2004, you suggested that anyone who was involved in leaking the name of the covert CIA operative would be fired."