Is it possible to disable login to CRM for specific user and allow only soap api access with admin rights?

It would be nice to be able to have an API user that does not use existing users. Using an existing front end user is not practical.

I need to create a user with admin access,
Do not want that user to login to CRM and access CRM,
but need to allow that user to create entries using SOAP API.
User is created only for SOAP API purpose.
Is it possible ?

When i use SOAP with CAS authentication, i could not login. Are there any way to by pass CAS when i use CAS authentication. ? Im using this method to login with CAS Authentication.