The two rivals will meet at Anfield for the first time since the release of the independent Hillsborough report earlier this month.
Both clubs have called for the end of distasteful chants relating to the Hillsborough disaster, and other tragedies which have the affected the respective clubs, including Heysel and the Munich air crash.
In Ferguson’s letter, which will be given to United supporters at Anfield this Sunday, the United boss called on the club’s fans to show their respect for the 96 who perished at the fateful FA Cup semi-final in 1989.
Ferguson said: “The great support you gave the team here last season has seen our allocation back up to near-full levels. I want you to continue that progress today.
“But today is about much more than not blocking gangways. Today is about thinking hard about what makes United the best club in the world.
“Our rivalry with Liverpool is based on a determination to come out on top – a wish to see us crowned the best against a team that held that honour for so long.
“It cannot and should never be based on personal hatred. Just ten days ago, we heard the terrible, damning truth about the deaths of 96 fans who went to watch their team try and reach the FA Cup final and never came back.
“What happened to them should wake the conscience of everyone connected with the game.
“Our great club stands with our great neighbours Liverpool today to remember that loss and pay tribute to their campaign for justice.
“I know I can count on you to stand with us in the best traditions of the best fans in the game.”