(a) The head of each agency may provide for the advance payment of the pay, allowances, and differentials, or any of them, covering a period of not more than 30 days, to or for the account of each employee of the agency (or, under emergency circumstances and on a reimbursable basis, an employee of another agency) whose departure (or that of his dependents or immediate family, as the case may be) from a place inside or outside the United States is officially authorized or ordered—

(1) from a place outside the United States from which the Secretary of State determines it is in the national interest to require the departure of some or all employees, their dependents, or both; or

(2) from any place where there is imminent danger to the life of the employee or the lives of the dependents or immediate family of the employee.

(b) Subject to adjustment of the account of an employee under section 5524 of this title and other applicable statute, the advance payment of pay, allowances, and differentials is at rates currently authorized with respect to the employee on the date the advance payment is made under agency procedures governing advance payments under this subsection. The rates so authorized may not exceed the rates to which the employee was entitled immediately before issuance of the departure order.

(c) An advance of funds under subsection (a) of this section is recoverable by the Government of the United States or the government of the District of Columbia, as the case may be, from the employee or his estate by—

(1) setoff against accrued pay, amount of retirement credit, or other amount due to the employee from the Government of the United States or the government of the District of Columbia; and

(2) such other method as is provided by law.

The head of the agency concerned may waive in whole or in part a right of recovery of an advance of funds under subsection (a) of this section, if it is shown that the recovery would be against equity and good conscience or against the public interest.