The nominee for next commandant of the Marine Corps could be announced as soon as Wednesday afternoon, according to multiple sources inside the Pentagon.

The office is expected to become vacant this fall pending the confirmation of the current commandant, Gen. Joseph Dunford, to chair the Joint Chiefs of Staff. Dunford, 59, was nominated in early May to succeed the current chairman, Army Gen. Martin Dempsey, who is set to retire later this year. Dunford became commandant just last October.

Since then, the future leadership of the Marine Corps has remained unclear. And with congressional recess for the month of August fast approaching, time is running out to nominate and confirm Dunford's successor in time for the fall transitions.

Sources said they expected a nomination announcement prior to the July 4 holiday, which begins Friday.

The likely nominee for 37th commandant of the Marine Corps has been a closely guarded secret. Possible candidates include the Marines' two other four-star generals, assistant commandant Gen. John "Jay" Paxton and Gen. John Kelly, commander of U.S. Southern Command. But the field also includes a number of highly qualified three-star generals who could be promoted to assume the post.

Names rumored to be considered for the position include Lt. Gen. Robert Neller, commander of Marine Corps Forces Command; Lt. Gen. Thomas Waldhauser, director for Joint Force Development, J-7 for the Joint Staff; Lt. Gen. Ronald Bailey, director of Marine Corps Plans, Policies and Operations; and Lt. Gen. Kenneth Glueck, commanding general of Marine Corps Combat Development Command.

The pending announcement could also include a nomination for 34th assistant commandant of the Marine Corps. Paxton, 64, has served as ACMC since December 2012, working with Dunford and his predecessor, Gen. James Amos.

Dunford's confirmation hearing before the Senate Armed Services Committee has already been set for July 9; a hearing to confirm his yet-to-be-named successor is also likely to take place this month.