i would let them know I think they are a nice person and enjoy their friendship. I have also said I am not trying to be rude or hurt your feelings. I just want to be honest and respectful because I would want people to be honest with me. I would let them know that I just am not interested in them in anything other than just friendship and nothing more and I hope they aren't unset with me I just don't feel the same.
Because guys are generally cowards in being honest with these things, they would be more likely to leave you hanging if they weren't interested - because they would not want to hurt you by saying no. That's their logic. They do not realise it hurts us more by leaving us guessing.
Woman are more honest and straightforward with communication and will just tell you no.
So I think if they leave you hanging it's a bad sign. It's much better to set the person straight.