I think he may just be very very shy, and be worried that he won;t kiss you properly. He didn;t say something involving the dreaded 'just friends' words, which is encouragin.
I know you won't think like that, but put yourself in his shoes, he is frightened you won't like him any more.
Next time, be more subtle. Give him a big grin, hold eye contact, say something like "I don't bite ..." and kiss him very gently on the mouth. If he doesn't respond, don't worry, he may be busy trying not to pass out or burst into tears with stress!
If his body language shos you that he is really not comfortable with what you are doing, you may have to accept that either he is a very slow learner, or he is just not that keen, but doesn;t know how to say so nicely.
Good luck - keep us posted.