David Beckham still fears Sir Alex Ferguson

He might be the most famous footballer on the planet. He might be a lavishly decorated elder statesman of the football world. He is even going to become a club owner in the United States in the near future. But at 37 years old, David Beckham admits that Sir Alex Ferguson still frightens him.

"You can see the aggression still. It scares me when I watch him on telly.

"He's always going to be that person. He has got that aggression. It will never go away from him as a manager. It's one of the reasons why he is respected like he is, but he has got that tender side as well. Not always, but he does have it and it's one of the reasons I had the relationship with him over the years and that I have now."

It is more than 20 years since Ferguson gave Beckham his Manchester United debut at Brighton in the FA Cup and both are still hungry to compete at the very top long after many had expected them to retire.

Beckham is steeling himself for one last big club challenge while Ferguson has twice deferred retirement and does not seem to be losing any of his desire.

"Looking at him on the sidelines I think he can go on forever," Beckham said. "It's impossible to say that he's ever going to stop. He continues to defy people and continues to defy an age limit in being a manager because he's the best. It's as simple as that.

"It was amazing to see him being honoured [with a statue outside Old Trafford] and you hear from players who have played for him what respect they have for him as a person and as a manager."

That respect was strained during Beckham's final days at United in 2003. Ferguson dropped him from the first team and after his team lost to Arsenal in the FA Cup kicked a boot that accidentally hit Beckham and cut him above the eye. They have rebuilt their relationship since, however, and Beckham hopes to become a Manchester United ambassador after he has finished his playing career.

That might not be as imminent as expected. Asked who he thought would retire first, Ferguson or himself, Beckham said: "I don't know. I want to continue playing as long as possible. As long as I can get around the field and feel I can play at a high level, I will."

That could mean playing into his 40s, assuming he avoids injury. Beckham admits watching former Manchester United team-mates Paul Scholes and Ryan Giggs still playing in the top flight gave him added incentive.

"It's nice to see them still playing at United," he said. "I'm 37, the same age as Scholesy, although Giggsy is even older than me. Me and Scholesy grew up together and played with Giggsy and it is great to see them still playing. I know when Scholesy stepped away he came back and regretted stopping. I want to continue to play for as long as my legs will take me."

Beckham is yet to disclose which club he will be joining but will clarify his position after the MLS Cup final. In the coming weeks he will also announce whether he is going to buy into an MLS expansion franchise or whether he will become part of the ownership structure at LA Galaxy. He is excited by the prospect of proving himself all over again.

"Wherever I've gone it's been a big deal throughout my career. Whether it's been going on loan to AC Milan, or leaving Manchester United for Real Madrid, or Real to here - it's always been big news," he said. "This next move will be a move that is about the football. That has never been any different.

"People say some of the moves have been about money but my answer is always the same that my career has never been about money. I'm not money motivated, I just want to play for the best team and with the best players."