Obama made his decision last Friday after a series of meetings over the past two weeks, it said, quoting senior administration officials.
The White House said the president will make an announcement on Hagel’s resignation late Monday morning.
Hagel, a 68-year-old Republican, took office in February 2013.
Analysts said that Obama’s decision on cabinet change appears to be an effort by the White House to show that it is sensitive to critics who have pointed to stumbles in the government’s early response to several national security issues, including the Ebola crisis and the threat posed by the Islamic State.