Hmm. Maybe he lost his balls in the war. It happens. They say being ball-less makes lovemaking a challenge. Or maybe he's about to be deported and knows it. If that's the case, though, seems like he'd want to marry you, if only to get his green card and be able to stay in the U.S.
Honestly, I have no idea what he means. Guys say stupid stuff sometimes. Did you ask him? When does he say it, when you're talking about getting more serious/married?
Maybe there's a reason behind it, but to me it just sounds like a bullshit excuse not to commit, as you suspect. I'd say move on, but you really need to find out what he means, if anything. If he's truly blowing you off and that's the best line he can come up with, then be glad to be rid of someone so unimaginative and lame.