Is there a way to disable user import in user federation when user logs in as LDAP/Active Directory user

I have user federation setup with Active Directory. The setup is such that the users aren’t all synced. The users will only import with a GET user request or GET token for the Active Directory user. Is there a way to disable the importing users on login? I want admin users to be able to manually import the users from AD, but not have users imported when someone attempts to login as an Active Directory user that hasn’t been imported yet.