If you’ll always want to be more than friends with him then you’ll have to let him go. He’ll obviously never see you as anything more than that. The only reason he still wants you to be his friend right now is purely a selfish reason and I suggest you don’t get stuck in this trap. In all honesty, I wouldn’t put myself through it. You’re just gonna get more attached to him and in the end he’ll move on anyway without giving you a single thought and you’ll be stuck trying to get over him.
At least you tried to tell him how you feel, so there’s no wondering "what if"in the future.