 -- The Obama administration is giving an unprecedented number of political appointees top diplomatic positions, a move that has long frustrated career Foreign Service officials but has become a renewed point of contention this week with the departure of Deputy Secretary of State Bill Burns, the only career foreign service officer in the top echelons of Foggy Bottom leadership.

Burns, who served more than three decades as a diplomat, announced earlier this week that he would be heading to the Carnegie Endowment for International Peace. His replacement has not yet been announced. The most talked-about candidates are Deputy National Security Adviser Tony Blinken or current Undersecretary of State for Political Affairs Wendy Sherman, both of whom would be political appointees.

It’s actually the norm for a political appointee to get the deputy slot. In the in the 41-year history of that position, Burns is the exception to the rule. But career officials say their wider concern is political appointees’ total takeover of all the top State Department positions, not only at the deputy level but also at the next-highest level, the undersecretary for political affairs slot, or the “P” position.

And even Burns, a seasoned diplomat who had recently helped in secret talks to get Iran to the negotiating table over its nuclear program, recognized the prevalence of political appointees serving in the White House’s National Security Council and alluded to frustration among the career ranks in a parting letter he wrote for Foreign Policy.

“The revolution in communications technology and the increasing role of both the National Security Council staff and other agencies over successive administrations have tended to bring out the more passive (or sometimes passive-aggressive) side of the State Department,” Burns wrote.

These are the kinds of concerns that Robert Silverman, the president of the American Foreign Service Association, made up of Foreign Service officers, says he’s hearing from his members.

“They care deeply about who their leadership is. They also care deeply about who their direct supervisor is. And here in Washington, that is increasingly people from outside the system with no experience in this position who take a lot of special handling,” Silverman told ABC News.

He noted that the top positions are not only concerned with the issues that the secretary of state works on, such as ISIS, Iran and North Korea, but also more the more mundane tasks that keep the department running, like those of the passport agency or child custody cases.

“We’re not opposed to political appointees -- it’s important to bring in outsiders with fresh perspectives,” he added. “It’s just completely out of balance.”

Another reflection of that lack of balance cited by AFSA and others is the ratio of political appointees to career officers that President Obama has chosen to serve as foreign ambassadors. In his second term, 41% of his ambassadorial appointees have been political, versus 58% career. His record over both terms is 64% career, 35% political -- second only to the record of George W. Bush, for whom political appointees counted as 36% of his total ambassadorial nominations.

But State Department spokesperson Jen Psaki rejected the notion that the influx of political appointees in the top leadership positions represented a lack of emphasis on the Foreign Service.

“While it would be inappropriate to speculate about pending decisions and nominations about the Department’s senior leadership, everyone should rest assured knowing that the Secretary doesn't just respect but reveres the institution that is the Foreign Service,” she said, adding that Secretary of State John Kerry is the son of a foreign service officer and has appointed more career officers in assistant secretary positions than “at any time in recent memory.”