The National Bank shall provide such financial assistance as it may consider necessary by way of making to State co-operative banks, regional rural banks, loans and advances repayable on the expiry of fixed periods not being less than eighteen months and not exceeding seven years against such securities as may be specified, in this behalf, by the National Bank and such loans or advances may be made for agriculture, rural development or such other purposes as the National Bank may, from time to time, determine:
     Provided that no loan or advance shall be made under this section to a State co-operative bank unless such loan or advance is fully guaranteed as to the repayment of the principal and payment of interest, by the State Government but such guarantee may be waived by the National Bank, if other security to the satisfaction of the National Bank is furnished, or if, for reasons to be recorded by it in writing, the National Bank is satisfied that the guarantee or other security is not necessary.