I don't think you can at present. The problem is that there needs to be a way for the page to get the "time" from the embedded video in order to synch.
There may be a way though using Javascript but you would need to be pretty clever with JavaScrip/ActionScript to get it to work.
Easiest way would be to screencapture the video of theembedded video (using Jing or Camtasia) and attach as an MP4 but only if you have copyright permissions to do this...