windows 7 - reg delete gives me "access is denied" but regedit delete is ok

I need to delete a key from a command line. So I wanted to use reg delete "the key to be deleted" /f but I get ERROR: access is denied.

From the same login session (the same user) I am able to delete the key without any troubles from regedit.exe that is not run as administrator.

I cannot use runas command to execute reg that I believe would be to solution because in fact I want to use reg to delete registry entry for administrator profile so runas works again. More info in my other question Windows7 corrupted profile - prevention exists?