I was this guy once. You have to break, possibly indefinitely. Sorry.
He won't get over you unless you give him A LOT of space. This might be hard and take time to get right, but you have to try. If you are not interested, then you cannot be friends. Trust me, this is the best solution. If you continue, you will create a long-term hell for both of you.
You've got to remember - cutting it off early is less painful for him. If you continue to be friends (depending on what you're like), he will be led on and the result will either be ugly for both of you or very hard on him. I could have saved literally years of pain if me and this girl just cut it off from the get go. Instead we tried to be friends and eventually it just couldn't work. You need to communicate with him though. He can't read your thoughts so if you do this, it might be a complete mystery to him as to why unless you explain.
Think longer-term, you remain friends (he will hide it but still like you) and you get a boyfriend? Then what happens? This will kill him if you've been close friends up until that point. It will be a disaster. Your boyfriend will hate this guy and be jealous of him. And your friend will hate you.
I appreciate this is not the answer you want, but life is not easy and sometimes you have to take decisions that seem pretty bad but are actually good in the long-run. This is one of those. And it requires sacrifice for both of you. Of course, neither of you may be able to do it. In which case, you may have to let it runs it course until it explodes into a huge argument.
So - meet up, explain you need to talk. Tell him. And leave it at it. But be nice about it. Support him. But don't remain close friends. At least not until he is over you - which could be anything from months to years - you'll probably 'feel' a different vibe when he is over you.
Posted from TSR Mobile