Washington ? Presidential adviser Karl Rove won’t be a criminal defendant in the CIA leak case, but he could still end up being grilled in court as a witness.

Special Counsel Patrick Fitzgerald could question Rove about whether the Bush administration compromised a CIA officer’s identity to retaliate against a political critic.

Still, Rove and the White House could breathe a sigh of relief Tuesday after the prosecutor told Rove’s lawyer he wouldn’t seek a federal indictment against the political operative.

Rove has been identified as a likely defense witness in next year’s trial of I. Lewis “Scooter” Libby, Vice President Dick Cheney’s former chief of staff. Libby has been charged with lying to the FBI and a federal grand jury about how he learned about Valerie Plame’s CIA status and what he told reporters about it.

If Libby’s defense attorneys summon Rove to testify, Fitzgerald can cross-examine him about a host of issues, including a July 2003 conversation Rove had with syndicated columnist Robert Novak days before Novak published Plame’s name.

Aboard Air Force One Tuesday, President Bush praised Fitzgerald. “It’s a chapter that has ended,” Bush said. “Fitzgerald is a very thorough person. I think he’s conducted his investigation in a dignified way.”

President Bush's Deputy Chief of Staff Karl Rove was told Tuesday by prosecutors that he won't be charged with any crimes in the investigation into the leak of a CIA agent's identity.

The president said White House officials would remain mum about the leak and the results of the investigation. “I think it’s going to be important for you all to recognize there’s still a trial to be had,” he said to reporters. “And those of us involved in the White House are going to be very mindful of not commenting on this issue … because of the Libby trial.”

At the White House, Rove was all smiles, as he usually is, as he carried out his normal routine. With Chief of Staff Joshua Bolten in Iraq with Bush, Rove ran the senior staff meeting.

While a cloud may have been lifted from its top political operative, the White House’s embarrassment over the Plame leak has not ended. The administration faces the possibility of a parade of current and former top officials being called to testify during Libby’s trial, starting with Cheney.

In court filings, Fitzgerald has described a White House campaign – led by Cheney – to discredit Plame’s husband, former U.S. Ambassador Joseph Wilson, after he wrote an opinion piece in The New York Times in July 2003 that accused the administration of twisting intelligence on Iraq to justify the war.

Fitzgerald has not ruled out calling Cheney, who cut out Wilson’s article with a pen knife and scrawled questions on it wondering whether Plame sent her husband on a “junket” to Niger to determine the accuracy of allegations that Iraq had tried to buy material to make a nuclear weapon.

Sen. Charles Schumer, D-N.Y., one of the first senators to call for an independent investigation of the leak, said, “We have faith that Prosecutor Fitzgerald will continue to pursue this case and turn over every other stone and follow every lead, no matter how high they take him.”