After once dismissing the newly-rich City as "noisy neighbours," Ferguson believes the Abu Dhabi-owned club have emerged as the next serious threat to United's dominance of the English footballing landscape.
"We have to get used to playing Manchester City in important games," Ferguson told reporters. "They are not going away.
"If we are going to be contesting for league titles regularly -- and I think we will be doing -- it will become just as important as the Liverpool game.
"Maybe not in terms of emotion because the Liverpool-United games are emotional. But there is certainly an importance which, at this moment in time, supercedes the Liverpool games.
"They are our direct opponents now. Manchester City are up against us to win titles. That is what our focus is on, the team who can stop us winning."
The countdown to one of the most eagerly-awaited Manchester derbies of all-time is under way, with leaders United three points clear of second-placed City with three games of the season remaining.
In what has been an enthralling title race, City topped the table for most of the campaign before United opened up an eight-point lead earlier this month after winning eight league games in a row.
But a stuttering run of form by United, which included a 1-0 defeat at relegation-threatened Wigan and a 4-4 home draw with Everton after leading 4-2, has allowed their big-spending neighbours back in.
"It's not a cup final because there are games to go after it, but it's an important game and I think it could decide the title," Ferguson said.
"I don't even say I can look forward to it.
"But I'm up for it and I'm prepared for it and I think my players will be prepared for it, so hopefully we'll be ok."
Ferguson, who reported no fresh injury concerns, added: "I suppose when the fixture came out at the start of the season all roads pointed to this game. It was inevitable really.
"We're smarting from throwing that game away last week but in the context of our history we have always expected it.
"We make it hard for ourselves. Our poor supporters have been subjected to that drama for years and years. God knows what they're like now, but hopefully we'll make up for it on Monday."
City seriously embarrassed United 6-1 at Old Trafford in the league earlier in the season, but Ferguson insists that will count for nothing when the teams meet.
"We are where we are. It doesn't matter what's happened before, the build-up to the game and who's dropped points and who hasn't dropped points. It's really all down to this game.
"Whatever has happened in the past is in the past."
City manager Roberto Mancini, who has spent millions of pounds assembling a team capable of winning the league, said last week that United would win the title despite watching his side reduce the gap at the top.
Ferguson said: "He probably wants to take pressure off his own players.
"It's not going to change our approach.
"We know the exact situation we're in. We're in a better postion than Man City. They have to win. We can draw but my attitude will be trying to win."