(a) An employee selected for training by, in, or through a nongovernment facility under this subchapter shall agree in writing with the Government before assignment to training that he will—
(1) continue in the service of the Government after the end of the training period for a period at least equal to the length of the training period unless he is involuntarily separated from the government service; and
(2) pay to the Government, if he is voluntarily separated from government service before the end of the period for which he has agreed to continue in the service of the Government—
(A) the amount of the additional expenses incurred by the Government in connection with his training; and
(B) the amount of any wages received by him during any leaves of absence with pay granted for the purpose of taking training.
(b) If an employee, except an employee relieved of liability under any provisions of this subchapter, fails to fulfill his agreement to pay to the Government a sum equal to the amount of the additional expenses of training and of wages paid while on leave of absence with pay, such sum is recoverable by the Government from the employee or his estate by—
(1) setoff against accrued pay, compensation, amount of retirement credit, or other amounts due the employee from the Government; and
(2) such other method as is provided by law for the recovery of amounts owing to the Government.