Manchester United manager Sir Alex Ferguson has claimed that his "passion for football" during European nights prevents him from retiring.

The 71-year-old, who has been in charge of the illustrious Premier League club for 27 years, will lead his side into tonight's Champions League second-leg clash against Real Madrid for a spot in the quarter-finals.

"People ask me why I don't retire after so many years in the game but how could anyone with an ounce of passion for football in their soul voluntarily walk away from the opportunity to be involved in this type of occasion?" Ferguson told tonight's match programme.

"This is what it is all about - a packed Old Trafford, the floodlights on, the pitch glistening and two of the greatest and romantic clubs in the game about to do battle."

The last-16 tie currently sits at 1-1 from the first leg at the Bernabeu.