Defense articles and defense services shall be sold or leased by the United States Government under this chapter to friendly countries solely for internal security, for legitimate self-defense, for preventing or hindering the proliferation of weapons of mass destruction and of the means of delivering such weapons, to permit the recipient country to participate in regional or collective arrangements or measures consistent with the Charter of the United Nations, or otherwise to permit the recipient country to participate in collective measures requested by the United Nations for the purpose of maintaining or restoring international peace and security, or for the purpose of enabling foreign military forces in less developed friendly countries to construct public works and to engage in other activities helpful to the economic and social development of such friendly countries. It is the sense of the Congress that such foreign military forces should not be maintained or established solely for civic action activities and that such civic action activities not significantly detract from the capability of the military forces to perform their military missions and be coordinated with and form part of the total economic and social development effort: Provided, That none of the funds contained in this authorization shall be used to guarantee, or extend credit, or participate in an extension of credit in connection with any sale of sophisticated weapons systems, such as missile systems and jet aircraft for military purposes, to any underdeveloped country other than Greece, Turkey, Iran, Israel, the Republic of China, the Philippines and Korea unless the President determines that such financing is important to the national security of the United States and reports within thirty days each such determination to the Congress.