A U.S. federal judge has refused to dismiss criminal charges against Vice President Dick Cheney's former aide, Lewis Libby, in connection with the leaking of a CIA operative's identity.

Libby has been indicted on five counts of perjury, obstruction of justice and lying to the FBI in the wake of the leak.  Lawyers for Libby had challenged the authority of Special Counsel Patrick Fitzgerald to handle the case, saying he had been given too much power.

A federal judge in Washington said the delegation of authority to Fitzgerald was lawful.

Libby's trial is scheduled to begin in January 2007.  

On Wednesday, President Bush's political adviser Karl Rove testified for the fifth time before a federal grand jury investigating the CIA leak.

A newspaper columnist in 2003 revealed the name of CIA operative Valerie Plame, shortly after Plame's husband publicly questioned President Bush's arguments for going to war in Iraq. 

The columnist said two administration officials identified Plame.  It is a crime for an official to knowingly reveal a CIA operative's identity.

Some information for this report was provided by AP and Reuters.