Before I load you down with techniques, I think we better examine your feeling of concern.
If you feel worried that revealing your romantic feelings for him would hurt the friendship, then you better listen to those feelings and figure out where they are coming from. The feelings can be coming from inside yourself, from him, or from a combination of both. Let's examine these possibilities.
It is very common to receive what is called 'induced' feelings from others. This means that we humans actually pick up other peoples' feelings, sort of like picking up radio waves. Whenever a feeling arises, it is always good to ask yourself if the feeling you have is being induced by another person. In other words, you need to find out if he is sending you an overt or covert message that says, 'Don't develop romantic feelings for me. That would ruin our friendship.'
To figure out if this is so, ask yourself, do I have reason to believe that he wouldn't be receptive to a romantic involvement with me? Do I have reason to believe that he wouldn't be open to maintaining our friendship after he learns that I have a romantic interest in him?
When you answer these questions, you will have an idea about what you suspect his issues are. When you approach, you would use your induced feelings and ask him questions like, 'Why do I feel afraid that if I told you that I have romantic feelings for you that our friendship would be ruined.' You get the idea.
Now, to get back to you. I spoke about the possibility that the feeling of fear may be coming from you. That is, this situation may be triggering unfinished business for you. You may have issues around rejection and abandonment. You may have been disappointed and frustrated in previous relationship dating as far back as your first family. You may have learned that you can't have the kind of responses that you want from others, which could explain why you might believe that he couldn't possibly like you back. You may have also learned from past experience that not only can't you have what you want, but that you get punished, dropped, etc. when what you desire doesn't happen to match what the other person wants.
This could explain your fear that he would drop the friendship with you if he isn't interested in more. You should never be punished for telling him or anyone else that you care. He may not want more than friendship, but that shouldn't ruin the friendship, so long as you are comfortable with remaining friends with someone for whom you deeply care.
If you are all right with keeping the friendship, then he should be O. K. with it too. The only reason that I could think that he wouldn't be O. K. with staying friends after you reveal your true feelings is that he would feel uneasy or guilty for not giving you what you truly want. Hence, he might want to break the friendship to escape those uncomfortable feelings.
However, I can't stress this point enough, if you can live with a friendship, then he should be fine. Once you dissect the feelings involved, and figure out which feelings are coming from you, and which are coming from him, you will know how to proceed.
I hope that he is ready to become involved with you.