Two sources with knowledge of the situation didn't provide any other details, CNN reported Tuesday.
Crocker was appointed ambassador to Afghanistan July 25. In 2002, Crocker was tasked with reopening the U.S. Embassy in Kabul after the Taliban were forced out of power, his State Department biography indicated.
Crocker was ambassador to Iraq 2007-09, and served as ambassador to Pakistan from 2004-07.
The State Department previously announced Cameron Munter, U.S. ambassador to Pakistan, also is expected to leave his post this summer.