For an Ambassador to be able to begin performing his duties, the receiving State (of residence) must first of all give its consent (agréement) to the sending State about the chosen diplomatic agent.
If the request is refused (the diplomat being considered a “persona non grata”), the receiving State is not required to explain why: Art. 4 of the 1961 Vienna Convention.
This is the phase after agréement, when granted. It is a ceremony in which the Chief of Mission presents the “Credential letters” (document certifying that the agent is authorised by his government to perform the duties of Ambassador) to the Head of the receiving State. Only then is the Ambassador accredited, and may begin to perform his duties.
The date of presentation of Credentials also determines the seniority of an Ambassador and the order of precedence to be adopted among the various Mission Chiefs.
Who new Ambassador presents Credential Letters to:
- Embassies to Italy: to the President of the Republic
- Embassies to Holy See: to the Pope
- Embassies to San Marino: to Captains Regent
- Embassies to the Sovereign Military Order of Malta: to Prince and Gran Maestro of the Order
- Embassies to FAO: to FAO Director General