This a very sticky situation. I need some serious advice?

I am Nigerian-American and I a met Nigerian guy who has been in the states for only 3 yrs. I met him some months ago and we got be very fond of each other. Our friendship has gotten so serious and intense that we are contemplating a relationship. I've never felt so loved. HOWEVER, he has a girlfriend aboard waiting for him to come back to marry her. You see, he only came here 3 years ago to work and hasn't gone back since then. He is now a perm. resident. Before coming here, he promised his girlfriend he would come back and marry her. She has been faithful and so has he. Until he met me, he hasn't been with anyone else in the 3 yrs he's been here. He told me about her when we met but I didn't think we were going to be romantically involved so I ignored it. But now we are in a bit of a snitch. He doesn't deny still loving her, but he says he has never had the feelings he has for me for anyone else before. He doesn't want to hurt the girl back home (his family is fond of her and can't wait for him to marry her) but he doesn't want me to let go. He's confused and so am I. The communication between him and the girl back home is dwindling and I feel bad. So I decided to take myself out of the picture. He is hurt and confused. What am I to do? I can see this guy in my life for a long time.