The Oscar picked up by Orson Welles for the film Citizen Kane is going under the hammer in the US.The 1941 classic is considered to be the director's best work to date, and its Academy Award is expected to fetch anything up to a $1million (£491,838).Sotheby's senior vice president of Collectibles Lee Dunbar, said: "The most comparable Oscar that's ever been sold to date is the David O Selznick award for Best Picture for Gone With the Wind - that was sold by Sotheby's back in 1999."That was estimated between $200-300,000 (£98,000-148,000) but it sold for $1.5m (£737,552)."Considering the great importance of this movie, and the fact that this is the only Oscar out of nine that was won by this movie, we feel that $800,000-1.2m (£393,000-590,078) is a very fair estimate."Dunbar said the auction will be held on December 11.© Independent Television News Limited 2007. All rights reserved.