How to add delete command for GEF in coolbar

Question

I need to define the toolbar delete command over plugin.xml for the perspective. I'm using the following code and for undo, redo, zoom in, zoom out works. Only for the delete command won't work. Where do i wrong?

            <command
              commandId="org.eclipse.ui.edit.redo"
              icon="icons/arrow_redo.png"
              label="Redo"
              style="push">
           <visibleWhen
                 checkEnabled="false">
              <with
                    variable="activeWorkbenchWindow.activePerspective">
                 <equals
                       value="GEF1.perspective">
                 </equals>
              </with>
           </visibleWhen>
        </command>
        <command
              commandId="org.eclipse.ui.edit.delete"
              icon="icons/cross.png"
              label="Delete"
              style="push">
           <visibleWhen
                 checkEnabled="false">
              <with
                    variable="activeWorkbenchWindow.activePerspective">
                 <equals
                       value="GEF1.perspective">
                 </equals>
              </with>
           </visibleWhen>
        </command>

PS:The delete command over the ActionBarContribution works fine.