I would be quite careful, friendship of similar nature can easily turn... well... funny.
I admit I am not the ideal person to discuss these kinds of problems with as I have never had any relationship yet but I do have an experience with a "friendship" that had gone fishy and eventually evaporated (and admittedly, I am quite glad it did, all things considering).
A dull story ensues: I used to know this guy, originally through an online book club, who sort of enjoyed talking to me about books, movies, computer games and stuff like that, I was about sixteen initially with him being ten years older than myself. It turned into a friendship of a kind over the years and when I got older (say, early 20s for myself), we began to discuss what troubled us in the life and tried to give each other some sort of support when the other one was in a bit of trouble for one reason or another. He knew I was sort of lonely and constantly hoping to find a date (sadly enough, that never happened). I, on the other hand, knew he didn't look for an actual relationship, preferring to live a mostly unencumbered life that allowed him to spend his money exclusively on his hobbies and to find solitude any time he fancied it (which was quite often, him not being the most sociable person around). I eventually learned, however, that he was seeing an older woman (about 15 year older than himself) on a semi-regular basis, one who was supposedly unhappily married (but not wanting to get a divorce, preferring to cheat on her husband while enjoying some other benefits of the married life), who sometimes came to visit him (she apparently kept on telling her husband she was going on business trips). Even though I knew this, I kept on telling myself that this was no concern of mine and that - since I wanted nothing more of him than to discuss new sci-fi TV series and travel shows and to chat about troubles at school or work - I was not to be judgemental towards his sex life, though it involved secrecy, deceit and other aspects of adultery. A few years ago, the guy started hinting that although he didn't love me, he sort of fancied me and that he would like to add me into his no-attachment sex life routine, imlying that he didn't get it as often as he would like (since the aforementioned lover of his lived quite far away) and that since I had no sex life of my own, it would certainly be great for both of us... despite the fact he knew it very well that I was only longing for an actual relationship (not for "secret" sex sessions with no strings attached of the kind he wanted), for a bit of love and for commitment. I was kind of offended and sort of disgusted as I really didn't want anything of this sort. I told him quite politely that this was really not my cup of tea. Any friendship that seemed to have worked for eight years or so quickly evaporated after this discussion and I was left with sort of mixed feelings - had the guy (at least initially) actually enjoyed talking to me and being supportive to my school troubles, or had he been just trying to groom me (an overweight girl with ehm... very limited dating opportunities) into a live toy for casual, unattached sex? I don't know.
I don't actually think about it very much these days but this problem of yours has sort of reminded me of this experience. You should clearly voice what are YOUR priorities - if he doesn't accept that you have no desire to date him/sleep with him/whatever, he does NOT actually care about you that much, he is only trying to achieve HIS goal without taking into acount what do you actually wish for, I think...