Standard Chartered will face a further three years of being under scrutiny from US authorities, after it was fined over £400m in 2012 for breaching American sanctions on Iran.The company announced on Wednesday that it has agreed to extend the deferred prosecution agreements (DPAs) entered into in December 2012 with the US Department of Justice and the New York County District Attorney's Office.The DPAs will be extended by a further three years to December 2017.StanChart said the agreement acknowledged that it has taken "a number of steps" to comply with the requirements of the original DPAs.These steps include implementing "more rigorous" US sanctions policies, training staff and putting measures in place to block payment instructions for countries subject to US sanctions laws and regulations."The agreement also indicates that the group is co-operating with an ongoing US sanctions-related investigation, but that additional time is needed to complete the investigation and determine whether any violations have occurred," the bank said.The stock was more or less flat at 944.3p by 08:07.