Rove entered a federal courtroom in Washington on Friday and left in the afternoon after four hours with a prosecutor specially assigned to the case, Patrick Fitzgerald.

"The special counsel has not advised Mr Rove that he is a target of the investigation and affirmed that he has made no decision concerning charges," Rove's lawyer Robert Luskin said in a statement.

"The special counsel has indicated that he does not anticipate the need for Mr Rove's further cooperation," the statement said.

Fitzgerald has tried for two years to find out who in the Bush administration identified CIA agent Valerie Plame, and the grand jury will decide whether a federal crime was committed.

Outing US agent

The case dates back to July 2003, when a conservative commentator with close ties to the Republican party, Robert Novak, published Plame's name.

"The special counsel has not advised Mr Rove that he is a target of the investigation and affirmed that he has made no decision concerning charges"

Robert Luskin,
Karl
Rove's lawyer

The CIA agent is the wife of Joseph Wilson, a former US ambassador who publicly questioned the Bush administration's justification for the war in Iraq.

Under US law, revealing the identity of an undercover CIA agent is a federal crime, though it remains unclear if the Plame case fell into that category.

The opposition Democrats called the leak an act of political revenge and demanded the White House reveal who had revealed the agent's name.

Political revenge

Wilson promptly pointed to Rove as the likely source. "At the end of the day, it's of keen interest to me to see whether or not we can get Karl Rove frog-marched out of the White House in handcuffs," Wilson said.

"And trust me, when I use that name, I measure my words," he added.

Suspense has been building over whether Rove, known as the mastermind behind Bush's political strategy and election campaigns, will be indicted or emerge unscathed.

The prosecutor has called in numerous officials from the Bush administration to testify and sent a journalist from The New York Times to prison for refusing to reveal who she spoke to in the White House.

Reporter Miller spent 85 days in 
jail for not cooperating  

The reporter, Judith Miller, who never wrote a story, was freed last month after 85 days in jail. She said her source gave her permission to discuss their conversation before a grand jury.

Miller has identified one of her sources as Vice-President Dick Cheney's chief of staff, Lewis "Scooter" Libby.

Another reporter, Matthew Cooper of Time magazine, said in July that Rove told him Wilson's wife was a CIA agent.

Bush has described Rove, 54, as the "architect" of his victorious re-election campaign last year. He has earned a reputation for political savvy and for employing sometimes ruthless tactics against his opponents.

Any indictment of Rove would deliver a damaging blow to Bush, who is already facing the lowest approval ratings of his presidency.