Cross account S3 access with Step Function Map ItemReader

Hi,

I currently have a state machine definition and am trying to update it so my distributed map reads objects from an s3 bucket in another account. I noticed in the documentation there's a warning: "Make sure that your Amazon S3 buckets are under the same AWS account and AWS Region as your state machine." for the ItemReader

Does this mean it isn't possible to do provide a bucket name and prefix to the ItemReader from another account? If so, how should I approach this situation?

Thanks, Harry