If you obtained your lawful permanent resident through your United States citizen wife then you can apply for naturalization to become a U.S. citizen pursuant to section 319 of the Immigration and Nationality Act after being a lawful permanent resident for a period of 3 years. However, to be eligible to apply under section 319, you and your wife have to live in marital union at the time of the filing of your naturalization application. Since you have indicated you have been separated from your wife for the last two years, you will not be eligible to apply for citizenship under section 319. Instead, you will be eligible for naturalization under section 316 and that requires you to be a lawful permanent resident for a period of 5 years before being eligible to apply for naturalization.
Answered on Jul 16th, 2012 at 8:26 AM