WIF call (SAML) of WCF REST protected service from Javascript (jQuery)

Question

I have doubts as to whether this is possible, but I hope that someone out there will have a deeper understanding of mechanics than I am.

We plan to host a clean javascript form on a SharePoint site that is protected using ADFS. This form should call the WCF REST service. We want to use the same FedAuth cookie / SAML token issued to the user from ADFS in the WCF service for authentication, but so far I really have not found a way to pass it using javascript.

So, to break it down, what do you call WIF / SAML protected WCF REST service from javascript?