HTTP monitor: error starting tunnel (Access denied)

I want to put SoapUI between a web service, only available on HTTPS, and the client that I am debugging. As I understand it, the Proxy mode won't do because its socket can't handle SSL/TLS. The HTTP Tunnel mode, however, can't start when fed with a HTTPS url and complains of "Access denied". A quick Google search showed that there's a "Security" tab that needs to be configured with a keystore, a truststore and even the SSL client keys.

I wonder why such a heavy setup is required. Can't HTTP tunnel simply receive a plain HTTP request and forward it to a HTTPS endpoint?