LTM https monitor via proxy

How to setup https monitor via webproxy? I would like to load-balance traffic to internet via F5 and webproxy nodes. But I need to actvely monitor https response from particural service in Internet. Using curl from bash I got sucessful response: curl -k -x https://webservice.com/

But when I try to setup https monitor it does not work:

CONNECT https://webservice.com/ HTTP/1.1\r\nHost: webservice.com\r\n

I could setup scripted monitor but maybe we can use standard https monitor?