(a) Acceptance.—An officer who is appointed to a higher grade under section 20239 of this title is considered to have accepted the appointment on the date on which the appointment is made unless the officer expressly declines the appointment.

(b) Oath.—An officer who has served continuously since taking the oath of office prescribed in section 3331 of title 5 is not required to take a new oath upon appointment to a higher grade under section 20239 of this title.