The administration of US President Donald Trump is removing dozens of ambassadors appointed under his predecessor's government as part of a broad reshuffle to align the diplomatic corps with its foreign policy priorities.
The heads of mission, mostly career diplomats, have been notified that they must leave their posts by mid-January, according to the American Foreign Service Association, which represents State Department employees.
US media reports on Monday said ambassadors from 30 countries, appointed by the administration of Joe Biden, will be affected, particularly in Africa.
While it is customary for an administration to reshuffle ambassadors appointed to strategic posts or capitals and to appoint donors or supporters, such a sweeping change is unusual before a career diplomat's term ends or their successor is appointed.
The AFSA said it had received "credible reports from our members in diplomatic posts around the world that multiple career ambassadors, appointed during the Biden administration, have been directed by phone call to vacate their posts by January 15 or 16".
"No explanation was given for these recalls," the association added in its post on Facebook.
"Removing senior diplomats without cause undermines US credibility abroad and sends a chilling signal to the professional foreign service: experience and an oath to the Constitution take a backseat to political loyalty."
Association spokeswoman Nikki Gamer told Reuters that abrupt, unexplained recalls "reflect the same pattern of institutional sabotage and politicisation our survey data shows is already harming morale, effectiveness and US credibility abroad".
The State Department declined to respond to Ms Gamer's comments. A senior State Department official said on Monday that changing ambassadors was "a standard process in any administration".
"An ambassador is a personal representative of the President, and it is the President's right to ensure that he has individuals in these countries who advance the America First agenda," the official said.
The official did not confirm the details of the dismissals, or which countries were affected.
In his second term, Mr Trump and his Secretary of State Marco Rubio have overhauled American diplomacy to focus priorities such as combating illegal immigration, and cutting foreign aid and diversity policies.
Mr Rubio has overseen the dismissal of hundreds of personnel in the State Department, and Mr Trump has placed loyalists as key ambassadors.
