Restrict backend page access by group

I am looking for a plugin that will allow me to restrict access to pages on the backend based on Group. In other words, Group A can only view and and edit pages created by members of Group A. Group B can only view and and edit pages created by members of Group B. New pages should be associated with the group(s) that they are members of. Again, this only pertains to the backend admin interface. On the front end, all pages should be viewable by all site visitors.

Thanks for any feedback.