EXT JS Store with external URL

Hey guys,
 
I'm building an EXT JS project with a grid. Its store is defined with the following:
 

createStore     :  function() {
       var me = this;
       me.createDataModel();
       var store = Ext.create("Ext.data.Store", {
           model       :  "tescoModel",
           id          :  "tescoStore",
           autoLoad    :  true,
           remoteSort  :  true,
           pageSize    :  20,
           proxy       :  {
               type            : "ajax",
               url             : "http://www.techfortesco.com/groceryapi_b1/restservice.aspx",
               limitParam      : undefined,
               startParam      : undefined,
               simpleSortMode  : true,
               pageParam       : undefined,
               noCache         : false,
               actionMethods   : {
                   method  : "POST"
               },
               reader           : {
                   type            : "json",
                   root            : "Products",
                   totalProperty   : "TotalProductCount"
               }
          }
       });

 
This however is not returning anything at all, it won't even make a connection to http://www.techfortesco.com....
I believe that extjs only allows to make connections to internal links (e.g. /techfortesco).
 
Is it possible for extjs to create a store from an external link? Am I doing something wrong?
 
Thanks