The US State Department/Immigration website is at
www.ins.usdoj.gov/

Check it out and see what is required.

Hint: My husband and I are American citizens who have adopted from China, so we have had to deal with INS a lot. It is not fun. When folks who are adopting from overseas have problems with INS (mostly INS being ssslllloooowww) they contact their Congressman for help. You don't have a congressman, but your prospective employer/sponsor does! If the employer is really hurting for an employee with skills such as yours, sometimes that can help.