How to translate RectTransform to Transform

I am using iTween to move and ease my UI, but I cannot find a way to translate the RectTransform's position to a transform.position.

Here's my example script:

 #pragma strict
     
     private var rt : RectTransform;
     var uiButton : UI.Button;
     var vector3 : Vector3;
     
     function Start () 
     {
         rt = uiButton.GetComponent(typeof (RectTransform)) as RectTransform;
     }
     
     function Update () 
     {
         if(Input.GetKeyDown(KeyCode.Space))
         {
             iTween.MoveAdd(uiButton.gameObject, iTween.Hash("y", vector3.y, "time", 2, "easeType", iTween.EaseType.easeInOutQuad));
         }
     }

I set the vector3 variable as 100 and it goes to the world space 100, not the recttransform 100.