(a) An Executive agency to which any officer or employee of the Department of State is detailed, assigned, or otherwise made available, shall reimburse the Department for the salary and allowances of each such officer or employee for the period the officer or employee is so detailed, assigned, or otherwise made available. However, if the Department of State has an agreement with an Executive agency or agencies providing for the detailing, assigning, or otherwise making available, of substantially the same numbers of officers and employees between the Department and the Executive agency or agencies, and such numbers with respect to a fiscal year are so detailed, assigned, or otherwise made available, or if the period for which the officer or employee is so detailed, assigned, or otherwise made available does not exceed one year, or if the number of officers and employees so detailed, assigned, or otherwise made available at any one time does not exceed fifteen and the period of any such detail, assignment, or availability of an officer or employee does not exceed two years, no reimbursement shall be required to be made under this section. Officers and employees of the Department of State who are detailed, assigned, or otherwise made available to another Executive agency for a period of not to exceed one year shall not be counted toward any personnel ceiling for the Department of State established by the Director of the Office of Management and Budget.

(b) For purposes of this section, "Executive agency" has the same meaning given that term by section 105 of title 5.