A top U.S. diplomat wrote in a letter made public on Wednesday that the State Department is struggling to recruit new leaders amid the poor morale brought on by the Trump administration—leading to new concerns about the country's role on the world stage.

In an essay entitled "Time to Ask Why" in the monthly newsletter of the American Foreign Service Association (AFSA), Ambassador Barbara Stephenson wrote, "There is simply no denying the warning signs that point to mounting threats to our institution—and to the global leadership that depends on us."

More than half of the department's career ambassadors have left their posts since President Donald Trump entered office in January, while other high-ranking officials have also retired or quit in record numbers. As Zack Beauchamp of Vox.com wrote, "The numbers reveal that American diplomacy, the backbone of U.S. global influence, is in a state of near collapse."

As the administration looks to cut the State Department's budget by nearly a third, Secretary of State Rex Tillerson has also imposed a hiring freeze as he attempts to create a more "efficient" State Department—tasking an outside consulting firm with interviewing employees to determine changes that might need to be made in the agency.

"These numbers are hard to square with the stated agenda of making State and the Foreign Service stronger," Stephenson wrote. "The talent being shown the door now is not only our top talent, but also talent that cannot be replicated overnight. The rapid loss of so many senior officers has a serious, immediate, and tangible effect on the capacity of the United States to shape world events."

In addition to the loss of scores of civil servants who would help to represent the U.S. in its relations with other countries, the department currently lacks an Assistant Secretary of State. Trump has dismissed concerns about the department's inability to fill its highest ranks, saying in an interview with Fox News last week, "I'm the only one that matters."

The ambassador expressed further concerns about a lack of enthusiasm for diplomatic work outside the department. While more than 17,000 Americans applied for the Foreign Service in 2016, that number has dropped by more than half this year.

"As the shape and extent of the staffing cuts to the Foreign Service at State become clearer, I believe we must shine a light on these disturbing trends and ask 'why?' and 'to what end?'" wrote Stephenson.