REUTERS/Gary Cameron
Carter's announcement is expected later Thursday.
It rebuffs arguments from the Joint Chiefs of Staff chairman that the Marine Corps should be allowed to exclude women from certain front-line combat jobs, citing studies showing that mixed-gender units aren't as capable as all-male units.
A senior defense official says all the services will have to begin putting plans in place by April 1.
The official was not authorized to discuss the matter publicly and spoke on condition of anonymity.
Previously, General Joseph Dunford, the Chairman of the Joint Chiefs of Staff contended that some combat jobs should stay male-only, reportedlysubmitting a report about five-inches thick outlining why he believes women should not be allowed to compete for certain Marine infantry and front-line jobs.
Dunford was, however, the only service cheif to issue such a recommendation.
Earlier this year, First Lt. Shaye Haver of Copperas Cove, Texas, and Capt. Kristen Griest of Orange, Connecticut became the first two females to graduate from one of the military's most challenging courses, the Army's elite Ranger School.
In early October, Carter told the troops at Naval Air Station Sigonella in Sicily, "You have to recruit from the American population. Half the American population is female... So I'd be crazy not to be, so to speak, fishing in that pond for qualified service members."