WASHINGTON, Dec 31: The United States on Wednesday appointed a special counsel to investigate allegations that the White House purposely leaked the identity of a CIA agent to silence her husband.

The husband, a former US ambassador, was critical of the Bush administration's Iraq policy. Deputy Attorney General James Comey told reporters in Washington that Attorney General John Ashcroft had withdrawn himself from supervising the investigation.

Mr Ashcroft had refused to appoint a special counsel in September when the CIA asked the Justice Department to appoint an independent counsel to lead the inquiry.

Mr Ashcroft insisted that as attorney general he should lead the investigation, but later changed his mind when critics said his supervision of the process would be a conflict of interest.

The Justice Department has now appointed a Chicago lawyer, Patrick Fitzgerald, as special counsel to conduct the investigation.