The Foxes are two points clear at the top and with a game in hand over nearest rivals Tottenham Hotspur, who closed the gap by beating Aston Villa on Sunday.
Despite the competition, Ferguson believes Claudio Ranieri's side will secure the title even before playing against United in their antepenultimate game of the campaign on May 1.
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When asked of Leicester's title chances at a Cheltenham Festival preview lunch, he said: "Of course they can [win the Premier League]. I believe they will win it with three games to spare."
The Scot continued to praise the club's recruitment, especially so the likes of assistant manager Steve Walsh.
"The most influential person in the Premier League has been Steve Walsh."
Walsh, who is also Leicester's Head of Recruitment, was responsible for bringing Jamie Vardy, Riyad Mahrez and N'Golo Kante to the club, all of whom have been resounding successes in the East Midlands.
The Foxes next face league strugglers Newcastle United on Monday night at the King Power Stadium before travelling to Crystal Palace this weekend.
Favourites to be relegated this term, Leicester have answered their critics - and surprised many in the process - under the guidance of Ranieri.
The Italian has instilled belief among his players since taking over last summer, so much so that their near-impossible dream of winning the Premier League looks increasingly likely.