The official said that John Bass's departure was long-planned and part of the normal rotation cycle, with American ambassadors typically serving in Kabul for only two years.
The State Department has named Ross Wilson as chargé d’affaires ad interim at the U.S. Embassy in Kabul until a new ambassador is confirmed. Wilson is expected to arrive in Kabul soon, according to the official.
Karen Decker, deputy chief of mission of the U.S. Embassy in Kabul, will serve as chargé d’affaires until Wilson's arrival, the official said.
In the wake of the announcement, Bass wrote in a series of posts on Twitter that he hopes Afghan leaders and citizens across the country will "find strength in unity, put aside their difference and work together to negotiate a political settlement with the Taliban."
The U.S. government has been negotiating with the insurgent group on and off over the past year in hopes of ending an 18-year war that started with an American invasion of Afghanistan just weeks after the terrorist attacks on Sept. 11, 2001.
In a farewell video posted to Facebook on Monday, Bass addressed Afghan leaders and citizens, saying, "As diplomats, we rarely stay long enough in a country to see and experience a whole story. We arrive in the middle of a tale, we learn about the chapters we missed and sometimes we become part of the story."
"None of us knows how this story, this chapter in the larger tale of this country and its people will end," he added. "It depends on your choices and whether you can work together and learn again to live together in peace, whether you can weave that tale together. The United States can and will help you, but we cannot choose your future or create it on your behalf. Only you can do that."