North American Free Trade Agreement (NAFTA) includes a program permitting
Canadian and Mexican visitors who are coming to the U.S. to do certain kinds
of work in the U.S. without having work visas.
take advantage of this opportunity, you must show written proof that you are
engaging in one of the occupations included in the program. A letter from
your employer verifying the work to be done will serve this purpose. If
relevant, you should also offer evidence that you are qualified for the job
with documents such as copies of diplomas or licenses.