We had earlier reported on the procedure to obtain a National Interest Exception (NIE).  A NIE is issued only under limited circumstances for H or L applicants. Applicants without a valid visa cannot apply for a NIE directly or ahead of the visa interview.

Travellers with a valid U.S. visa who believe they are eligible for the NIE should follow the procedure listed in the above link to apply for the exception so that they are able to travel to the U.S. without being stopped by the airline or by the U.S. Customs and Border Protection (CBP) at the airport or other U.S. port of entry.