Problem using rhevm-manage-domain tool to join AD domain

I have setup the rhevm server, and the hypervisor, I have virtual machines running on my single host and can usually connect to them (a bit iffy connecting with SPICE to RHEL and other linux machines but that's a matter for another discussion).

Now my problem is that I cannot add my AD domain to the config so I can assign users in our AD domain to guests hosted on the RHEV-H server. I am trying to use the following command:

rhevm-manage-domains -action=add -domain='office.domain' -user='Inter\Administrator' -interactive

but get error

Failure while testing domain office.domain. Details: Authentication Failed. Please verify the username and password.

The thing is if I needed to log in through Windows the username would appear as: 

"Inter\Admininistrator"

'Inter' being an alias pointing to the AD domain (office.domain), in which the user to do stuff in is Administrator.

Can anyone tell me if 'Inter\Administrator' should be able to work with this tool talking to AD, or would it have to appear differently? ("Inter-Administrator", "Inter:Administrator", maybe even just "Adminisatrator")... I've tried these variations without any luck so far, so maybe the problem is something else entirely?

Any assistance is appreciated.