A Government agency, at the request of the Secretary, may perform such technical or other services as such agency may be competent to render for the government of another country desirous of obtaining such services, upon terms and conditions which are satisfactory to the Secretary and to the head of the Government agency, when it is determined by the Secretary that such services will contribute to the purposes of this chapter. However, nothing in this chapter shall authorize the performance of services relating to the organization, training, operation, development, or combat equipment of the armed forces of a foreign government.