US President Barack Obama attends the Armed Forces Full Honor Review Farewell Ceremony for Obama at Joint Base Myers-Henderson Hall in Arlington, Virginia, January 4, 2017.
CNN  — 

President-elect Donald Trump’s transition team has told all ambassadors who are political appointees of President Barack Obama to vacate their overseas posts by Inauguration Day, refusing to provide even brief grace periods for special cases, several senior State Department officials and American diplomats said.

“Political” ambassadors often have close ties to the president or are major donors and almost always leave their post at the end of the term, while career ambassadors frequently remain in their posts.

In keeping with standard practices, the White House requested and received resignations from all politically-appointed chiefs of mission shortly after Election Day, several senior State Department officials told CNN.

But, in a break with precedent to consider grace periods on a case-by-case basis, a subsequent State Department cable sent last month to all non-career ambassadors instructed them to finish their service by January 20 “without exceptions,” the sources said.

The move, first reported by The New York Times, leaves the US without top envoys at key posts such as Britain, Germany, Canada, Japan and Saudi Arabia until President-elect Donald Trump nominates successors and they are confirmed, a process that could take months. In the meantime, the posts will be run by the highest-ranking career official until Trump nominates, and the Senate confirms, someone new.

The decision has also left diplomats scrambling to secure new visas, living arrangements and schools for their children, including Ambassador to Costa Rica Stafford Fitzgerald Haney, who diplomats say has four school-age children and a wife battling breast cancer. Mark Gilbert, the US ambassador to New Zealand told CNN he was denied a one-week extension after January 20 to finish packing his residence.

Past incoming administrations from both parties have granted exceptions on a case-by-case basis for ambassadors requesting to remain at post for weeks or months.

The exceptions are generally granted as a courtesy to ambassadors with school-age children or who have unique family situations, but are also occasionally made to help with continuity as the incoming administration seeks to fill a large number of postings at home and overseas.

Secretary of State John Kerry told CNN’s Wolf Blitzer that it is a “perfectly normal request” to political ambassadors to leave their post, noting that “all political appointees serve at the pleasure of the President of the United States.”

But Kerry added, “Some people ask for an extension for some reason or another. In some cases, it might make sense to think sensitively about that.”

In 2009, Obama granted several exceptions to Bush-era political ambassadors for work or personal reasons.

The State Department estimates that roughly 70% of US ambassadors are career appointees. Those ambassadors were not asked to tender resignation letters.

CNN’s Zahra Ullah contributed to this report.