Unable to use User Control inside Portlet control - This type of page is not served

[njain]

I want to use user control inside the portlet but getting an error

"This type of page is not served.".

If I give URL to the aspx page it works fine.

My question is is there is any way to call user control inside Porlet.

<ext:Portlet ID="Portlet4" Title="Dundas Chart" runat="server" Height="450">
       <Loader ID="Loader2" runat="server" Url="~/TestUserControl.ascx" Mode="Frame" />
 </ext:Portlet>

Thanks for your help.