JSF 2.1 Redirect Preserving error message

I have the following commandButton action method handler:

public String reject()
{
  //Do something
  addMessage(null, "rejectAmountInvalid", FacesMessage.SEVERITY_ERROR);

  redirectToPortlet("/xxx/inbox?source=pendingActions#pendingApproval");
}

public static void addMessage(String clientId, String key, Severity level, Object... objArr)
{
    FacesContext context = FacesContext.getCurrentInstance();
    FacesMessage message = null;
    String msg = getTextFromResourceBundle(key);
    if (objArr != null && objArr.length > 0)
        msg = MessageFormat.format(msg, objArr);
    message = new FacesMessage(msg);

    message.setSeverity(level);
    context.addMessage(clientId, message);
}

public static void redirectToPortlet(String urlToRedirect)
{
    FacesContext context = FacesContext.getCurrentInstance();
    ExternalContext externalContext = context.getExternalContext();

    try
    {
        PortletRequest portletRequest = (PortletRequest) externalContext.getRequest();
        ThemeDisplay themeDisplay = (ThemeDisplay) portletRequest.getAttribute("THEME_DISPLAY");
        String portalURL = themeDisplay.getPortalURL();
        String redirect = portalURL + urlToRedirect;
        externalContext.redirect(redirect);
    }
    catch (Throwable e)
    {
        logger.log("Exception in redirectToPortlet to the URL: " + urlToRedirect, VLevel.ERROR, e);
    }
}

When the page is redirected to "/xxx/inbox?source=pendingActions#pendingApproval", the error message I added is lost. Is there a way to preserve the error message in JSF 2.1?

Thanks Sri