400 and 200 response contributing to slow HTTPS connection

I'm debugging a slow SSAS connection over HTTPS using Basic Auth. Looking at the requests in fiddler I've noticed that for every request the AdomdClient sends the first response without any auth headers and receives a 400 response, then sends a request with the auth headers and receives a successful 200 response (see below). 

Is there someway to force the auth headers to be sent in the first request?

Thanks

Chris