Fergie in for the long haul

At 68, he is heading into his 24th season at Old Trafford where he has won 11 Premier League titles and two European Cups.

The short-term aim is to wrest the crown back from Chelsea after it pipped his side at the post last season.

He said: "A lot of factors come into most important things. I'm at the right club, it's a fantastic club, it demands a challenge all the time.

"Every day, every year there's the challenge of being at the top and that helps me. I think you need good natural energy and I've been blessed with that.

"I'm very fortunate about that so I'll keep going as long as my health keeps going. The same applies to every person. I'm 68 and so far my health's been standing up.

"If I have my health I can carry on. There will be a point when I do quit but I have absolutely no idea when that is.

"I tried that a few years ago and it was an absolute disaster. Agony. My wife made me change my mind and she was dead right.

"I think she was soon fed up with me in the house. Now when the time comes I think the club should be okay."

In an interview with CNN, Ferguson also defended the owners, the Glazer family, who have found themselves a target from the Green and Gold protest movement.

While United is the number on football club in the world on the Forbes Rich List, the large debt is what concerns supporters.

Ferguson said: "The debt has come through by the club being bought out by an owner. You know full well that when a business is bought it's usually bought with debt.

"Because it's a football club it seems to attract a more negative reporting from the media and from the fans. But Manchester United football club, when it went plc, it was always going to be bought.

"It was inevitable.

"So when a particular family like the Glazers have bought it, it's unfair they come in for criticism because anybody could have bought it.

"I have to say they've done their job well. They support myself, the manager, they've supported the players. I've never been refused when I've asked for money for a player.

"So what can I do other than carry on the way we're doing it and the way I'm allowed to carry on, I've no complaints."