Manchester United boss Sir Alex Ferguson admits he's frightened of retirement.

He said: "When I reached 60, I asked myself the question. I almost left.

"But I quickly realised, with my family, that it was a mistake. Today, I fear the idea of retiring. I have been on the train for so long that when I get off I fear my system will collapse.

"I have decided not to ask myself the question any more. Three things can make me stop. 1. My health. 2. If I don't take pleasure any more. 3. If I don't have the strength for new challenges any more.

"Each summer, I have a look at those three things. I go to my doctor first. I had a pacemaker set up four or five years ago.

"Today, I am playing the penalty shoot-out of my managerial career. I know that. The rest is decided between me and me.

"I see my doctor every summer. He says 'boss, you are 67. You will have more and more back pains. Getting up in the morning sometimes won't be easy.'

"This is the penalty shootout."