A number of senior career diplomats are leaving the State Department after the Trump administration accepted their resignations from presidentially appointed positions.

The State Department said Thursday that several senior management officials as well as a top arms control diplomat would be leaving. All had submitted their resignations prior to Donald Trump's January 20 inauguration as is required of officials holding jobs appointed by the president. They were not required to leave the foreign service but chose to retire or resign for personal reasons, the department said.

While none of the officials has linked his or her departure explicitly to Trump, many diplomats have privately expressed concern about serving in his administration given the unorthodox positions he's taken on many foreign policy issues.

Turnover among senior leadership during presidential transitions is not unusual, although the career diplomats who are leaving the foreign service entirely had served under both Republican and Democratic presidents.

More resignations are expected to be accepted as Trump's diplomatic team takes shape, according to the officials who were not authorized to discuss personnel matters publicly and spoke on condition of anonymity. The now vacant jobs will be filled by subordinates on an acting basis until their full-time appointments are named, the officials said.

Among those whose resignations have been accepted are Thomas Countryman, who had been serving as the acting undersecretary of state for arms control and international security. Others include Undersecretary for Management Patrick F. Kennedy; two assistant secretaries, Joyce Barr and Michele Bond; and Gentry Smith, who directs the Office of Foreign Missions. They had been willing to remain at their posts but had no expectation of staying, according to several State Department officials familiar with the resignations.

Other senior career diplomats to have left the State Department since Trump's election include Victoria Nuland, the former assistant secretary for European and Eurasian Affairs, and Gregory Starr, the assistant secretary for diplomatic security. Starr retired on Inauguration Day as did Lydia Muniz, a non-career political appointee who had run Overseas Building Operations.

Trump has yet to fill many top diplomatic jobs, including the deputy secretary roles. His nominee to be secretary of state, Rex Tillerson, is expected to be confirmed by the Senate next week.

Kennedy was relied upon by both Democrats and Republicans. He was tapped for the undersecretary post in 2007 by President George W. Bush and stayed on throughout President Barack Obama's term. His position oversees the department's budget and finances, security, global facilities and consular services.

Kennedy, a diplomat since 1973, was criticized for the department's insufficient security at the diplomatic post in Benghazi, Libya, where four Americans were killed in 2012. In testy congressional hearings, Kennedy defended then-Secretary of State Hillary Clinton's handling of the situation and insisted there was no "stand down" order to the U.S. military during the attack.

Bureau records also showed Kennedy asked for the FBI's help in 2015 to change the classification level of an email from Clinton's private server. The FBI ultimately rejected the request.