ambassador-at-large

An ambassador-at-large is either a diplomat, a secretary or a minister of the highest rank who is accredited to represent his or her country and their people internationally. Unlike an ambassador-in-residence who is usually limited to a country or embassy, the ambassador-at-large is entrusted to operate in several usually neighboring countries, a region or sometimes hold a seat in an international organization like the United Nations and the European Union. 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. https://en.wikipedia.org/wiki/Ambassador-at-large