Officers who are not included on the active duty promotion list may be promoted under regulations to be prescribed by the Secretary. These regulations shall, as to officers serving in connection with organizing, administering, recruiting, instructing, or training the reserve components and as to officers designated by the Secretary pursuant to this section, provide as nearly as practicable, that such officers will be selected and promoted in the same manner and will be afforded equal opportunity for promotion as officers of the corresponding grade on the active duty promotion list.