Manchester United manager Sir Alex Ferguson has warned Manchester City they could suffer "untold" damage if they lose the Premier League title race.

The derby rivals go into Sunday's final day of the season only separated by goal difference at the top of the table.

Leaders City host relegation-threatened Queens Park Rangers, while United travel to take on Sunderland at the Stadium of Light.

Ferguson has conceded it will take "something stupid" for United to beat City to the title, but he has also attempted to undermine the confidence of his club's 'noisy neighbors'.

"City have got to win, but it's an enormous challenge for them, because the disappointment of losing the game would be unbelievable," said Ferguson.

"It's untold at this moment in time what affect it could have on them.

"It's fantastic for the neutral, fantastic for the media, but agony for both clubs, more so for City if they lose it."

Ferguson, though, has admitted City will have taken a huge stride forward if they manage to complete their title quest.

If City beat QPR at the Etihad Stadium, it would complete an achievement worth recognizing for Blues boss Roberto Mancini, one that even Ferguson accepts goes far beyond merely assembling a squad at vast cost.

"To win the league is not easy," said Ferguson. "Many people underestimate how difficult it is to win the league.

"Of course, Roberto Mancini has had a big financial advantage over everyone, but you have still got to put a team on the pitch and pick the right players.

"The manager must take the most credit if you win the league over here, because when you have squads of players, trying to orchestrate the harmony in the place is very important.

"Making everyone feel they have played their part is not easy in the modern game. To win the league is a massive step forward for Mancini."