The Tannadice club have already revealed they are ready to sell Russell and they are considering a move to bring back David Goodwillie from Blackburn Rovers as a replacement.
Celtic and Italian side Catania have been linked with Russell as a result but Championship side Derby appear to be leading the race.
United boss Jackie McNamara said in the Daily Record: "I think the club are getting closer to agreeing a fee with Derby for Johnny.
"If they agree, it will then be down to the player. There's been a lot of speculation and I think it would be good if it were to be brought to a speedy conclusion."