Backup Database Role\permission in SQL Server 2005

I have 20+ databases on the SQL Cluster. How can I give a user the permission to backup any database without giving sysadmin access ?
I dont want to make the user dbo on all databases either.BACKUP DATABASE and BACKUP LOG permissions default to members of the sysadmin fixed server role and the db_owner and db_backupoperator fixed database roles.
If not you could take advantage to EXECUTE AS in this case.|||thanks Satya. I was hoping in SQL 2005, may be they had come up with something better. The only problem with db_backupoperator approach is that every time you add a new database to the server, thethe id needs to be given access to that database.