A question about xml in URL monitor in Applications Manager

Hello,

I would like to use the POST method in a URL monitor and submit an xml request. A form that the monitored server understands is like this:

xml=<?xml version="1.0" encoding="windows-1251"?><product>ProdCode</product>

However when I add such string as a Request parameter , monitoring does not work as expected. I used Network sniffer which shows that App Manager seems to delete content between first and last "equal" signs, so that the monitored server receives the string
xml="windows-1251"?><product>ProdCode</product>
The server does not understand the string.
Please advise if I can use such string as a Request parameter in URL monitor.

Thank you