Although he called it quits with the now 58-year-old singer, he claimed in his letter that he never meant to "hurt" her and offered out his hand for a possible friendship.
He explained: "I never meant to hurt you. As you can see I have grown both spiritually and mentally. It no longer matters how I'm perceived.
"Please understand my previous position as that of a young man with limited experience with a extremely famous sex symbol.
"I offer my friendship once again time this time much stronger and focused. If you are still interested I would like to further discuss this with you but some it couldn't wait. I felt compelled to tell you... just in case anything happened to 2 me."
The letter is set to go up for auction between July 19 and July 29 at Gotta Roll, according to TMZ, and the bids will start at US$100,000.
Following her relationship with Tupac, Madonna went on to have daughter Lourdes, 20, with ex-partner Carlos Leon, son Rocco, 16, with her ex-husband Guy Ritchie, and adopted four children; David, 11, Mercy, 11, Stelle and Estere, four.
- Bang! Showbiz