One IAM Role accros multiple AWS accounts

For security reasons, we have a pre-prod and a prod AWS account. We're now beginning to use IAM Roles for S3 access to js/css files through django-storage / boto.

While this is working correctly on a per account basis, now a need has risen where the QA instance needs to access one S3 bucket on a the prod account.

Is there a way to have one IAM role that can grant access to the pre-prod And prod S3 buckets? As I'm writing it seems impossible, but it never hearts to ask!