Diplomatic visas are used by diplomats and other government officials for travel to the United States. With the exception of a Head of State or Government who qualifies for an A visa regardless of the purpose of his or her visit to the United States, the type of visa required by a diplomat or other government official depends upon their purpose of travel to the United States.
The specific types of Diplomatic visas are:
To qualify for an A-1 or A-2 visa, you must be traveling to the United States on behalf of your national government to engage solely in official activities for that government. The fact that there may be government interest or control in a given organization is not in itself the defining factor in determining if you qualify for an A visa; the particular duties or services that will be performed, must be governmental in character or nature. Government officials traveling to the United States to perform non-governmental functions of a commercial nature or traveling, as tourists, require the appropriate visa, and do not qualify for diplomatic visas.
Foreign officials who are traveling to the United States on official business must obtain an A visa prior to their entry. They cannot travel on tourist’s visas, or visa free under the Visa Waiver Program.
Qualified A visa applicants traveling to the United States for assignments of less than 90 days will be issued visas annotated "TDY" (temporary duty).