Officials are expressing concern over a series of departures of high-ranking diplomats at the State Department, with one former official warning that "having so many vacancies in essential places is a disaster waiting to happen."

“These people either do not believe the U.S. should be a world leader, or they’re utterly incompetent,” Dana Shell Smith told The New York Times. Smith was the ambassador to Qatar until she resigned in June.

Aides for Tillerson have also reportedly depleted much of the department's diversity by firing most of the department's leading African-American and Latino diplomats.

“I don’t feel targeted as an African-American,” former Ambassador to Liberia and African Affairs secretary Linda Thomas-Greenfield told the Times. “I feel targeted as a professional.”

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Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE, the former CEO for ExxonMobil, has put a stop to most hiring at the department and fired top foreign service members, as well as many lower-tier diplomats whose work he deems unnecessary.

In a plan to push out nearly 2,000 staffers, Tillerson has offered a $25,000 incentive for diplomats to leave the department.

By December, the department will have reduced its two highest ranks of diplomats by nearly one half, from 39 to 19, while Tillerson has not filled or even nominated people for 34 of the 44 open positions created by the presidential transition, according to a count provided by the American Foreign Service Association to the Times.

The hiring freeze and departures of top-ranking officials elicited letters from Democrats on the House Foreign Affairs Committee and from Sens. John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (R-Ariz.) and Jeanne Shaheen Cynthia (Jeanne) Jeanne ShaheenSenate Democrats introduce bill to sanction Russians over Taliban bounties Trump-backed candidate wins NH GOP Senate primary to take on Shaheen Democratic senator urges Trump to respond to Russian aggression MORE (D-N.H.), saying that Tillerson's efforts are undermining America internally "as complex global crises are growing externally."

Democrats and some Republicans also recently protested President Trump's budget request that asked to slash the State Department's budget to $37.6 billion.