Open a XML File in a ModalDialog

Hi all

I am having a small problem.In my page i want to open a xml file in a modalDialog

So whats happening is in the javascript function 

function openModal()
{

 return window.showModalDialog(url, '', properties);

}
Where the URL is a XML file that will be transformed by a XSL stylesheet

The modal window is getting opened but it remains blank.

Is it that the showModalDialog will only understand html files.If so is
there any alternate way for us to open a model window.

Cheers

Jonas