Ambassador-at-large

An Ambassador-at-large is a diplomat, secretary, or a minister of the highest rank who is accredited to represent a country or organization and its people internationally.
Unlike an ambassador-in-residence, who is usually limited to a singular country or embassy, an ambassador-at-large is entrusted to operate in several usually neighboring countries, a region or sometimes hold a seat in an international organizations. In some cases, an ambassador-at-large may even be specifically assigned a role to advise and assist the state or a government in particular issues. Historically, presidents or prime ministers have designated special diplomatic envoys for specific assignments, primarily overseas but sometimes also within the country as an ambassador-at-large.
Furthermore, unlike an ambassador-in-residence, an ambassador-at-large was not forced to resign from Starfleet as was seen in the case of Commodore Robert April.