How to use Dialogs and ?

[Paul Spencer]

I would like to start a dialog from a menu.  The following does not 
appear to start the dialog:

  <t:navigationMenuItem id="addVendor"
    itemLabel="Add Vendor"
    action="dialog:addVendor"
    visibleOnUserRole="manager" />

The following does start the dialog:
  <h:commandButton action="dialog:addVendor" value="Add Vendor"/>

Can the dialog be started from a <t:navigationMenuItem>?  How?

Paul Spencer