It depends on how long you have known this person how long have you been friends two things you need to take into consideration befor you do anything
1. If you have been friends with this person for a while then you should be able to tell this person how you feel and if this person is any kinda of a friend they will be completely honest to you and if you two are really good friends then it should not really strenghten or weaken the friendship
2. If its an infatuation then that could make things ackward due to the fact that its not a little crush you could easily get over with time its a desire and then you would have to weigh the options and come to agreement on wiehter or not the friendship is worth more to you. Or if you think you could have a real relationship
My advice would be to read your friends emotions how they act toward you and how much they trust you also look for physical sign's if there are any real obvious sign's that this person feels the same then by all means go for it ,but if its unsure I would have to say hold off. Another good way to find were you stand with this person is to ask them what they think of you as a person and what you mean to them.