Sir Alex Ferguson will appeal against a Football Association charge of improper conduct, BBC Sport understands.The Manchester United boss said he had "feared the worst" when referee Martin Atkinson was appointed for Tuesday's game with Chelsea, which United lost.Ferguson added on MUTV: "You want a fair referee, or a strong referee anyway - and we didn't get that."He also has two matches of a four-game ban from last season hanging over him after remarks about referee Alan Wiley.Ferguson was angry over Atkinson's failure to dismiss Chelsea defender David Luiz for fouls on Javier Hernandez and Wayne Rooney after he had already been booked.He was further upset when Chelsea was awarded what he considered a "soft" penalty when Yuri Zhirkov fell under the challenge of Chris Smalling.If Ferguson's suspended ban is triggered, he will be suspended from the touchline for United's FA Cup sixth-round tie with Arsenal at Old Trafford on 12 March and the Premier League game with Bolton a week later and then whatever extra games if any are added on for his latest outburst.United's loss at Stamford Bridge pegged their lead over Arsenal back to four points, with the Gunners having played a game less.Arsenal could close the gap to one point with a home win over Sunderland on Saturday, with Ferguson's team playing Liverpool at Anfield on Sunday.Ferguson cancelled his customary pre-match news conference on Friday, in which he would have been expected to talk about Sunday's Premier League match against Liverpool.Source: BBC