WASHINGTON — Kiron Skinner, the State Department’s director of policy planning and one of the highest-ranking African-American women in the department, has been forced out of her job, according to administration officials.

Ms. Skinner took leave last September from serving as a professor at Carnegie Mellon University and as a researcher at the Hoover Institution, to join Secretary of State Mike Pompeo’s senior leadership team. Her small unit, one of the most storied inside the State Department, has been trying to develop a long-term strategy for dealing with the rise of China.

She was a disciple of Condoleezza Rice, a secretary of state and national security adviser under President George W. Bush, and has written widely on the foreign policy of the Reagan administration, among other topics.

She joins a long list of officials in the Trump administration who have been removed from their posts or who have resigned. But she is among the first of Mr. Pompeo’s small circle of influential aides. Mr. Pompeo is considered the most powerful cabinet member, the top-level adviser in the Trump administration who seems to have an uncanny ability to read and channel the president.