The Secretary of the Interior, or such official as may be designated by him, is authorized, until otherwise directed by Congress, to advance to the tribe or to pay out of any unobligated tribal funds of the Klamath Indians in the Treasury of the United States salaries and expenses of tribal officials or representatives (except the Klamath Loan Fund Board) at rates and/or limitations designated in advance by the Klamath General Council, or any governing body to which it may delegate such authority, and approved by the Secretary of the Interior: Provided, That the length of stay of representatives serving the tribe at the seat of government shall be determined by the Secretary of the Interior.