There is created within the Treasury a separate fund for guarantees which shall be available to the Administrator without fiscal year limitations as a revolving fund for the purpose of . All amounts received by the Administrator, including any moneys, property, or assets derived by him from his operations in connection with shall be deposited in the fund. All expenses and payments, excluding administrative expenses, pursuant to operations of the Administrator under shall be paid from the fund. Moneys in the fund not needed for the payment of current operating expenses or for the payment of claims arising under this part may be invested in bonds or other obligations of, or bonds or other obligations guaranteed as to principal and interest by, the United States; except that moneys provided as capital for the fund shall not be so invested.