On or about June 11 or 12, 2003, the Under Secretary of State orally advised Libby in the White House that, in sum and substance, Wilson's wife worked at the CIA and that State Department personnel were saying that Wilson's wife was involved in the planning of his trip.
There are 6 people who hold that title in the State Department. Here are the people who held the position of Under Secretary of State in June 2003:
John Robert Bolton
Under Secretary of State for Arms Control and International Security Affairs
Marc Isaiah Grossman
Under Secretary of State for Political Affairs
Grant S. Green
Under Secretary of State for Management
Charlotte L. Beers
Under Secretary of State for Public Diplomacy
Paula J. Dobriansky
Under Secretary of State for Global Affairs
Alan Phillip Larson
Under Secretary of State for Economic, Business, and Agricultural Affairs
Obviously, certain people are more likely candidates than others.