I need to send XML /  XML string to a web service cross domain.

I have a JavaScript function that creates the XML by selecting the fields on the page and formatting the values into the required XML document.  The HTML page is running on the users local machine but need to send the XML to a public secure (SSL) web service (ASMX) that has one argument of type string.  

I have tried to come up with a solution and the only one that is currently working is JSONP with GET.  But this results in the data being send as part of the query string and is in clear view, thus being intercept-able.  

Regards

Jaco