Revalidation or Renewal of a Visa

Nonimmigrant visa applicants who currently have a visa, and are seeking renewal or revalidation of their visa for future travel to the U.S. must apply abroad, generally in their country of residence.  The exception is renewal or revalidations of A, G, and NATO diplomatic and official visas (except A-3, G-5 and NATO-7), which continue to be processed in Washington and at the U.S. Mission to the United Nations in New York.

Source: U.S. Department of State.