The Dutchman has been prolific for the Premier League champions since making the controversial move, netting 39 goals in all competitions so far.
"The head-to-head talks I had with RVP many, many times convinced me I had to sell him," The Express quotes Wenger as saying.
"I think what was part of that is that RVP was convinced by the Dutch coach that was at Manchester United. That played a big part in that.
"It will be strange to see him in a United shirt because for me he is an Arsenal man. I took him as a very, very young player and we came together through very difficult periods. He became a world class player and for me he is an Arsenal player."
Van Persie will face his former club in this Sunday's league encounter at Old Trafford.