Scot admits England's top flight is "very difficult to win"
After falling to Chelsea on Tuesday, United sit four points ahead of second-placed Arsenal and ahead of Sunday's meeting with Liverpool, Ferguson has called on his side to maintain their title charge.
"Go back to 1998 when we were 12 points clear of Arsenal and threw that away," he told MUTV.
"There's no question if you don't have momentum in this part of the season you are going to struggle to win the league.
"You lose momentum and it can be very difficult for you."
The Scot also added his belief that the Premier League is very difficult to win when considering the sides that are battling for the title.
"It is what everyone expects, a very difficult league to win," he added.
"You've got Arsenal, Manchester City, ourselves, Chelsea and if we all start winning games...
"I said many weeks ago that whoever is most consistent will win the league."