The 36-year-old now-LA Galaxy man came close to a surprise loan move to Tottenham last season, but the deal failed to materialise.
And Beckham, who is due to face United in a friendly next week as part of a MLS All Stars team next week, has admitted why the switch to White Hart Lane did not happen.
The former England captain could not face the prospect of playing for any club other than United, with who he won the famous Treble in 1999 among a host of other titles.
Beckham said: "I have always said I have played for the biggest club in England and I wouldn't like to play against them (United).
"I am 36 and still feel good and fresh but I can't see it happening.
"The Tottenham thing didn't happen for a reason. I only want to be known as a Manchester United player and that's the way it will stay."