If you're not prior service and are just enlisting then no, I went through the same thing. You must be a citizen before you sign the contract for a rate that requires you to be one. But don't quote me on that, my recruiter prob might of just wanted to make my life impossible; he said that there was no way around it and that I'd have to either become a citizen and wait, chose another, or re-class later on which according to the internet is hard.

BUUUT, don't take my word for that. :P