(21)In accordance with Article 59(5) of Regulation (EU) No 909/2014, which includes an explicit reference to Article 46(3) of Regulation (EU) No 648/2012, bank guarantees or letters of credit, where appropriate, should be aligned to the CPSS-IOSCO Principles and meet similar requirements as those laid down in Regulation (EU) No 648/2012. These include the requirement that bank guarantees and letters of credit are fully collateralised by the guarantors. In order to preserve the efficiency of security settlement within the Union, however, when bank guarantees or letters of credit are used in relation to credit exposures that may arise from interoperable CSD links, appropriate alternative risk mitigants should be allowed to be considered as long as they provide an equal or higher level of protection than the provisions laid out in Regulation (EU) No 648/2012. This special treatment should only apply to bank guarantees or letters of credit protecting an interoperable CSD link and should cover exclusively the credit exposure between the two linked CSDs. Since the bank guarantee or the letter of credit protects the non-defaulting CSDs against credit losses, the liquidity needs of the non-defaulting CSDs should also be addressed by either a timely settlement of the guarantors' obligations, or alternatively, by holding qualifying liquidity resources.