In authorizing the performance of technical and other services under this subchapter, it is the sense of the Congress (1) that the Secretary shall encourage through any appropriate Government agency the performance of such services to foreign governments by qualified private American individuals and agencies, and shall not enter into the performance of such services to any foreign government where such services may be performed adequately by qualified private American individuals and agencies and such qualified individuals and agencies are available for the performance of such services; (2) that if such services are rendered by a Government agency, they shall demonstrate the technical accomplishments of the United States, such services being of an advisory, investigative, or instructional nature, or a demonstration of a technical process; (3) that such services shall not include the construction of public works or the supervision of the construction of public works, and that, under authority of this chapter, a Government agency shall render engineering services related to public works only when the Secretary shall determine that the national interest demands the rendering of such services by a Government agency, but this policy shall not be interpreted to preclude the assignment of individual specialists as advisers to other governments as provided under subchapter III of this chapter, together with such incidental assistance as may be necessary for the accomplishment of their individual assignments.