Multi-level Administration

Hi,

I want to be able to have multiple levels for administering users.

Level 1 admin will be able to add users for all other levels.
Level 2 admin will be able to add users only for Level 3 and Level 4.
Level 3 admin will be able to add users only for Level Level 4.

I actually have three levels of users:

managers
support
authenticated users

I want the support level to have admin permissions for authenticated users but not for managers.

Thanks