The Secretary of Agriculture is authorized to expend funds, available for agricultural conservation, adjustment, and land use programs, for the share of the United States as a member of the International Wheat Advisory Committee, the International Sugar Council, or like events or bodies concerned with the objectives of said program, together with traveling and other necessary expenses relating thereto: Provided, That expenditures under this authority shall not be made unless provision is made therefor in the applicable appropriation and the cost thereof is not in excess of limitations prescribed therein.