I like my best friend...but his best friend likes me!

I have a tiny problem. I really like this guy. And we are best friends now. Yes, we made out and stuff but that's it. Then another close friend of ours asked me out, which I sadly said no to. Then my best friend said he liked me but stopped because of...

this guy who asked me out. They are friends. I dont know if we are ever going to be more than just best friends now. We have an obvious attraction for each other...but can we get past this? At first he said we were only best friends but then we went a little further after that. What do I do? Oh and the guy who asked me out is leaving in less than a month to boot camp to join the marines. So...any suggestions? How can I ensure not to ruin our friendship but also tell him how I feel...
Thanks!!! Im 17

Women have a lot harder time with a guyfriend they like going out with another girlfriend, so it will probably not have any affect on their relationship.